diff --git a/middleware/requestLanguage.js b/middleware/requestLanguage.js
new file mode 100644
index 00000000..c7532fc9
--- /dev/null
+++ b/middleware/requestLanguage.js
@@ -0,0 +1,109 @@
+
+const _ = require('lodash');
+const logger = require( 'pelias-logger' ).get( 'api' );
+
+/**
+  this middleware is responsible for negotiating HTTP locales for incoming
+  browser requests by reading the querystring param 'lang' or 'Accept-Language' request headers.
+
+  the preferred language will then be available on the $req object:
+  eg. for '?lang=fr' or 'Accept-Language: fr':
+  ```
+  console.log( req.language );
+
+  {
+    name: 'French',
+    type: 'living',
+    scope: 'individual',
+    iso6393: 'fra',
+    iso6392B: 'fre',
+    iso6392T: 'fra',
+    iso6391: 'fr',
+    defaulted: false
+  }
+  ```
+
+  for configuration options see:
+  https://github.com/florrain/locale
+**/
+
+const locale = require('locale');
+
+/**
+  BCP47 language tags can contain three parts:
+    1. A language subtag (en, zh).
+    2. A script subtag (Hant, Latn).
+    3. A region subtag (US, CN).
+
+  at time of writing we will only be concerned with 1. (the language subtag) with
+  the intention of being compatible with the language standard of whosonfirst data.
+
+  whosonfirst data is in ISO 639-3 format so we will need to configure the library
+  to support all ISO 639-1 (2 char) codes and convert them to 639-1 (3-char) codes.
+
+  see: https://github.com/whosonfirst/whosonfirst-names
+**/
+const iso6393 = require('iso-639-3');
+
+// create a dictionary which maps the ISO 639-1 language subtags to a map
+// of it's represenation in several different standards.
+const language = {};
+iso6393.filter( i => !!i.iso6391 ).forEach( i => language[ i.iso6391 ] = i );
+
+// a pre-processed locale list of language subtags we support (all of them).
+const allLocales = new locale.Locales( Object.keys( language ) );
+
+// return the middleware
+module.exports = function middleware( req, res, next ){
+
+  // init an object to store clean (sanitized) input parameters if not initialized
+  req.clean = req.clean || {};
+
+  // init warnings array if not initialized
+  req.warnings = req.warnings || [];
+
+  // set defaults
+  var lang = language.en;
+  var locales, best, via = 'default';
+
+  // input language via query param
+  if( via === 'default' && req.query && req.query.lang ){
+    locales = new locale.Locales( req.query.lang );
+    best = locales.best( allLocales );
+    if( best.defaulted ){
+      req.warnings.push( 'invalid language provided via querystring' );
+    } else {
+      lang = language[ best.language ];
+      via = 'querystring';
+    }
+  }
+
+  // input language via request headers
+  if( via === 'default' && req.headers && req.headers['accept-language'] ){
+    locales = new locale.Locales( req.headers['accept-language'] );
+    best = locales.best( allLocales );
+    if( best.defaulted ){
+      req.warnings.push( 'invalid language provided via header' );
+    } else {
+      lang = language[ best.language ];
+      via = 'header';
+    }
+  }
+
+  // set $req.language property
+  req.language = _.clone( lang );
+  req.language.defaulted = ( via === 'default' );
+
+  // set $req.clean property in order to print language info in response header
+  req.clean.lang = {
+    name: req.language.name,
+    iso6391: req.language.iso6391,
+    iso6393: req.language.iso6393,
+    defaulted: req.language.defaulted
+  };
+
+  // logging
+  logger.info( '[lang] \'%s\' via \'%s\'', lang.iso6391, via );
+
+  next();
+};
diff --git a/package.json b/package.json
index e92c0018..98ad08e0 100644
--- a/package.json
+++ b/package.json
@@ -47,8 +47,10 @@
     "geojson": "^0.4.0",
     "geojson-extent": "^0.3.1",
     "geolib": "^2.0.18",
+    "iso-639-3": "^1.0.0",
     "iso3166-1": "^0.3.0",
     "joi": "^10.1.0",
+    "locale": "^0.1.0",
     "lodash": "^4.5.0",
     "markdown": "0.5.0",
     "morgan": "1.8.1",
@@ -62,6 +64,7 @@
     "pelias-text-analyzer": "1.7.2",
     "predicates": "^1.0.1",
     "retry": "^0.10.1",
+    "request": "^2.79.0",
     "stats-lite": "^2.0.4",
     "superagent": "^3.2.1",
     "through2": "^2.0.3"
@@ -74,7 +77,6 @@
     "nsp": "^2.2.0",
     "precommit-hook": "^3.0.0",
     "proxyquire": "^1.7.10",
-    "request": "^2.79.0",
     "semantic-release": "^6.3.2",
     "source-map": "^0.5.6",
     "tap-dot": "1.0.5",
diff --git a/routes/v1.js b/routes/v1.js
index 60e48172..8ee4173f 100644
--- a/routes/v1.js
+++ b/routes/v1.js
@@ -18,7 +18,8 @@ var sanitizers = {
 
 /** ----------------------- middleware ------------------------ **/
 var middleware = {
-  calcSize: require('../middleware/sizeCalculator')
+  calcSize: require('../middleware/sizeCalculator'),
+  requestLanguage: require('../middleware/requestLanguage')
 };
 
 /** ----------------------- controllers ----------------------- **/
@@ -108,6 +109,7 @@ function addRoutes(app, peliasConfig) {
     ]),
     search: createRouter([
       sanitizers.search.middleware,
+      middleware.requestLanguage,
       middleware.calcSize(),
       // 3rd parameter is which query module to use, use fallback/geodisambiguation
       //  first, then use original search strategy if first query didn't return anything
@@ -131,6 +133,7 @@ function addRoutes(app, peliasConfig) {
     ]),
     structured: createRouter([
       sanitizers.structured_geocoding.middleware,
+      middleware.requestLanguage,
       middleware.calcSize(),
       controllers.search(peliasConfig.api, esclient, queries.structured_geocoding, not(hasResponseDataOrRequestErrors)),
       postProc.trimByGranularityStructured(),
@@ -150,6 +153,7 @@ function addRoutes(app, peliasConfig) {
     ]),
     autocomplete: createRouter([
       sanitizers.autocomplete.middleware,
+      middleware.requestLanguage,
       controllers.search(peliasConfig.api, esclient, queries.autocomplete, not(hasResponseDataOrRequestErrors)),
       postProc.distances('focus.point.'),
       postProc.confidenceScores(peliasConfig.api),
@@ -165,6 +169,7 @@ function addRoutes(app, peliasConfig) {
     ]),
     reverse: createRouter([
       sanitizers.reverse.middleware,
+      middleware.requestLanguage,
       middleware.calcSize(),
       controllers.coarse_reverse(pipService, coarse_reverse_should_execute),
       controllers.search(peliasConfig.api, esclient, queries.reverse, original_reverse_should_execute),
@@ -184,6 +189,7 @@ function addRoutes(app, peliasConfig) {
     ]),
     nearby: createRouter([
       sanitizers.nearby.middleware,
+      middleware.requestLanguage,
       middleware.calcSize(),
       controllers.search(peliasConfig.api, esclient, queries.reverse, not(hasResponseDataOrRequestErrors)),
       postProc.distances('point.'),
@@ -202,6 +208,7 @@ function addRoutes(app, peliasConfig) {
     ]),
     place: createRouter([
       sanitizers.place.middleware,
+      middleware.requestLanguage,
       controllers.place(peliasConfig.api, esclient),
       postProc.accuracy(),
       postProc.localNamingConventions(),
diff --git a/test/ciao/autocomplete/language_default.coffee b/test/ciao/autocomplete/language_default.coffee
new file mode 100644
index 00000000..3e39e8db
--- /dev/null
+++ b/test/ciao/autocomplete/language_default.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/autocomplete?text=example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/autocomplete/language_header_invalid.coffee b/test/ciao/autocomplete/language_header_invalid.coffee
new file mode 100644
index 00000000..56941e3c
--- /dev/null
+++ b/test/ciao/autocomplete/language_header_invalid.coffee
@@ -0,0 +1,38 @@
+
+#> language
+path: '/v1/autocomplete?text=example'
+headers: 'Accept-Language': 'example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+json.geocoding.warnings.should.eql [ 'invalid language provided via header' ]
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/autocomplete/language_header_valid.coffee b/test/ciao/autocomplete/language_header_valid.coffee
new file mode 100644
index 00000000..aea8c28c
--- /dev/null
+++ b/test/ciao/autocomplete/language_header_valid.coffee
@@ -0,0 +1,38 @@
+
+#> language
+path: '/v1/autocomplete?text=example'
+headers: 'Accept-Language': 'fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  defaulted: false,
+  iso6391: 'fr',
+  iso6393: 'fra',
+  name: 'French'
+}
diff --git a/test/ciao/autocomplete/language_querystring_invalid.coffee b/test/ciao/autocomplete/language_querystring_invalid.coffee
new file mode 100644
index 00000000..65ead1fc
--- /dev/null
+++ b/test/ciao/autocomplete/language_querystring_invalid.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/autocomplete?lang=example&text=example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+json.geocoding.warnings.should.eql [ 'invalid language provided via querystring' ]
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/autocomplete/language_querystring_valid.coffee b/test/ciao/autocomplete/language_querystring_valid.coffee
new file mode 100644
index 00000000..4b267ff2
--- /dev/null
+++ b/test/ciao/autocomplete/language_querystring_valid.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/autocomplete?lang=fr&text=example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  defaulted: false,
+  iso6391: 'fr',
+  iso6393: 'fra',
+  name: 'French'
+}
diff --git a/test/ciao/place/language_default.coffee b/test/ciao/place/language_default.coffee
new file mode 100644
index 00000000..444b6254
--- /dev/null
+++ b/test/ciao/place/language_default.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/place?ids=geonames:venue:1'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/place/language_header_invalid.coffee b/test/ciao/place/language_header_invalid.coffee
new file mode 100644
index 00000000..142464d6
--- /dev/null
+++ b/test/ciao/place/language_header_invalid.coffee
@@ -0,0 +1,38 @@
+
+#> language
+path: '/v1/place?ids=geonames:venue:1'
+headers: 'Accept-Language': 'example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+json.geocoding.warnings.should.eql [ 'invalid language provided via header' ]
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/place/language_header_valid.coffee b/test/ciao/place/language_header_valid.coffee
new file mode 100644
index 00000000..639d3b72
--- /dev/null
+++ b/test/ciao/place/language_header_valid.coffee
@@ -0,0 +1,38 @@
+
+#> language
+path: '/v1/place?ids=geonames:venue:1'
+headers: 'Accept-Language': 'fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  defaulted: false,
+  iso6391: 'fr',
+  iso6393: 'fra',
+  name: 'French'
+}
diff --git a/test/ciao/place/language_querystring_invalid.coffee b/test/ciao/place/language_querystring_invalid.coffee
new file mode 100644
index 00000000..3783aa4c
--- /dev/null
+++ b/test/ciao/place/language_querystring_invalid.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/place?lang=example&ids=geonames:venue:1'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+json.geocoding.warnings.should.eql [ 'invalid language provided via querystring' ]
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/place/language_querystring_valid.coffee b/test/ciao/place/language_querystring_valid.coffee
new file mode 100644
index 00000000..3192e754
--- /dev/null
+++ b/test/ciao/place/language_querystring_valid.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/place?lang=fr&ids=geonames:venue:1'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  defaulted: false,
+  iso6391: 'fr',
+  iso6393: 'fra',
+  name: 'French'
+}
diff --git a/test/ciao/reverse/language_default.coffee b/test/ciao/reverse/language_default.coffee
new file mode 100644
index 00000000..659aa5c2
--- /dev/null
+++ b/test/ciao/reverse/language_default.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/reverse?point.lat=1&point.lon=2'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/reverse/language_header_invalid.coffee b/test/ciao/reverse/language_header_invalid.coffee
new file mode 100644
index 00000000..35cd83d1
--- /dev/null
+++ b/test/ciao/reverse/language_header_invalid.coffee
@@ -0,0 +1,38 @@
+
+#> language
+path: '/v1/reverse?point.lat=1&point.lon=2'
+headers: 'Accept-Language': 'example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+json.geocoding.warnings.should.eql [ 'invalid language provided via header' ]
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/reverse/language_header_valid.coffee b/test/ciao/reverse/language_header_valid.coffee
new file mode 100644
index 00000000..bca45c1a
--- /dev/null
+++ b/test/ciao/reverse/language_header_valid.coffee
@@ -0,0 +1,38 @@
+
+#> language
+path: '/v1/reverse?point.lat=1&point.lon=2'
+headers: 'Accept-Language': 'fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  defaulted: false,
+  iso6391: 'fr',
+  iso6393: 'fra',
+  name: 'French'
+}
diff --git a/test/ciao/reverse/language_querystring_invalid.coffee b/test/ciao/reverse/language_querystring_invalid.coffee
new file mode 100644
index 00000000..af1bff84
--- /dev/null
+++ b/test/ciao/reverse/language_querystring_invalid.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/reverse?lang=example&point.lat=1&point.lon=2'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+json.geocoding.warnings.should.eql [ 'invalid language provided via querystring' ]
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/reverse/language_querystring_valid.coffee b/test/ciao/reverse/language_querystring_valid.coffee
new file mode 100644
index 00000000..45f22e1b
--- /dev/null
+++ b/test/ciao/reverse/language_querystring_valid.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/reverse?lang=fr&point.lat=1&point.lon=2'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  defaulted: false,
+  iso6391: 'fr',
+  iso6393: 'fra',
+  name: 'French'
+}
diff --git a/test/ciao/search/language_default.coffee b/test/ciao/search/language_default.coffee
new file mode 100644
index 00000000..eb85265c
--- /dev/null
+++ b/test/ciao/search/language_default.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/search?text=example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/search/language_header_invalid.coffee b/test/ciao/search/language_header_invalid.coffee
new file mode 100644
index 00000000..0035956c
--- /dev/null
+++ b/test/ciao/search/language_header_invalid.coffee
@@ -0,0 +1,38 @@
+
+#> language
+path: '/v1/search?text=example'
+headers: 'Accept-Language': 'example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+json.geocoding.warnings.should.eql [ 'invalid language provided via header' ]
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/search/language_header_valid.coffee b/test/ciao/search/language_header_valid.coffee
new file mode 100644
index 00000000..4f3b958d
--- /dev/null
+++ b/test/ciao/search/language_header_valid.coffee
@@ -0,0 +1,38 @@
+
+#> language
+path: '/v1/search?text=example'
+headers: 'Accept-Language': 'fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  defaulted: false,
+  iso6391: 'fr',
+  iso6393: 'fra',
+  name: 'French'
+}
diff --git a/test/ciao/search/language_querystring_invalid.coffee b/test/ciao/search/language_querystring_invalid.coffee
new file mode 100644
index 00000000..cdfe0195
--- /dev/null
+++ b/test/ciao/search/language_querystring_invalid.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/search?lang=example&text=example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+json.geocoding.warnings.should.eql [ 'invalid language provided via querystring' ]
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  name: 'English',
+  iso6391: 'en',
+  iso6393: 'eng',
+  defaulted: true
+}
diff --git a/test/ciao/search/language_querystring_valid.coffee b/test/ciao/search/language_querystring_valid.coffee
new file mode 100644
index 00000000..8b389efd
--- /dev/null
+++ b/test/ciao/search/language_querystring_valid.coffee
@@ -0,0 +1,37 @@
+
+#> language
+path: '/v1/search?lang=fr&text=example'
+
+#? 200 ok
+response.statusCode.should.be.equal 200
+response.should.have.header 'charset', 'utf8'
+response.should.have.header 'content-type', 'application/json; charset=utf-8'
+
+#? valid geocoding block
+should.exist json.geocoding
+should.exist json.geocoding.version
+should.exist json.geocoding.attribution
+should.exist json.geocoding.query
+should.exist json.geocoding.engine
+should.exist json.geocoding.engine.name
+should.exist json.geocoding.engine.author
+should.exist json.geocoding.engine.version
+should.exist json.geocoding.timestamp
+
+#? valid geojson
+json.type.should.be.equal 'FeatureCollection'
+json.features.should.be.instanceof Array
+
+#? expected errors
+should.not.exist json.geocoding.errors
+
+#? expected warnings
+should.not.exist json.geocoding.warnings
+
+#? language
+json.geocoding.query['lang'].should.eql {
+  defaulted: false,
+  iso6391: 'fr',
+  iso6393: 'fra',
+  name: 'French'
+}
diff --git a/test/unit/middleware/requestLanguage.js b/test/unit/middleware/requestLanguage.js
new file mode 100644
index 00000000..6252e589
--- /dev/null
+++ b/test/unit/middleware/requestLanguage.js
@@ -0,0 +1,322 @@
+
+var middleware = require('../../../middleware/requestLanguage');
+module.exports.tests = {};
+
+var DEFAULTS = {
+  defaulted: true,
+  iso6391: 'en',
+  iso6392B: 'eng',
+  iso6392T: 'eng',
+  iso6393: 'eng',
+  name: 'English',
+  scope: 'individual',
+  type: 'living'
+};
+
+module.exports.tests.defaults = function(test, common) {
+  test('default language', function(t) {
+
+    var req = {};
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, DEFAULTS, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, []);
+
+      t.end();
+    });
+  });
+  test('both querystring & header invalid', function(t) {
+
+    var req = {
+      headers: { 'accept-language': 'foobar' },
+      query: { 'lang': 'foobar' }
+    };
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, DEFAULTS, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, [
+        'invalid language provided via querystring',
+        'invalid language provided via header'
+      ]);
+
+      t.end();
+    });
+  });
+};
+
+module.exports.tests.invalid = function(test, common) {
+  test('headers: invalid language', function(t) {
+
+    var req = { headers: {
+      'accept-language': 'invalid language'
+    }};
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, DEFAULTS, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, [
+        'invalid language provided via header'
+      ]);
+
+      t.end();
+    });
+  });
+  test('query: invalid language', function(t) {
+
+    var req = { query: {
+      lang: 'invalid language'
+    }};
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, DEFAULTS, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, [
+        'invalid language provided via querystring'
+      ]);
+
+      t.end();
+    });
+  });
+};
+
+module.exports.tests.valid = function(test, common) {
+  test('headers: valid language - french', function(t) {
+
+    var req = { headers: {
+      'accept-language': 'fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5'
+    }};
+
+    var expected = {
+      defaulted: false,
+      iso6391: 'fr',
+      iso6392B: 'fre',
+      iso6392T: 'fra',
+      iso6393: 'fra',
+      name: 'French',
+      scope: 'individual',
+      type: 'living'
+    };
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, expected, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, []);
+
+      t.end();
+    });
+  });
+  test('query: valid language - french', function(t) {
+
+    var req = { query: {
+      lang: 'fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5'
+    }};
+
+    var expected = {
+      defaulted: false,
+      iso6391: 'fr',
+      iso6392B: 'fre',
+      iso6392T: 'fra',
+      iso6393: 'fra',
+      name: 'French',
+      scope: 'individual',
+      type: 'living'
+    };
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, expected, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, []);
+
+      t.end();
+    });
+  });
+
+  test('headers: valid language - english', function(t) {
+
+    var req = { headers: {
+      'accept-language': 'en'
+    }};
+
+    var expected = {
+      defaulted: false,
+      iso6391: 'en',
+      iso6392B: 'eng',
+      iso6392T: 'eng',
+      iso6393: 'eng',
+      name: 'English',
+      scope: 'individual',
+      type: 'living'
+    };
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, expected, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, []);
+
+      t.end();
+    });
+  });
+  test('query: valid language - english', function(t) {
+
+    var req = { query: {
+      lang: 'en'
+    }};
+
+    var expected = {
+      defaulted: false,
+      iso6391: 'en',
+      iso6392B: 'eng',
+      iso6392T: 'eng',
+      iso6393: 'eng',
+      name: 'English',
+      scope: 'individual',
+      type: 'living'
+    };
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, expected, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, []);
+
+      t.end();
+    });
+  });
+};
+
+module.exports.tests.precedence = function(test, common) {
+  test('precedence: query has precedence over headers', function(t) {
+
+    var req = {
+      headers: { 'accept-language': 'fr' },
+      query: { 'lang': 'es' }
+    };
+
+    var expected = {
+      defaulted: false,
+      iso6391: 'es',
+      iso6392B: 'spa',
+      iso6392T: 'spa',
+      iso6393: 'spa',
+      name: 'Spanish',
+      scope: 'individual',
+      type: 'living'
+    };
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, expected, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, []);
+
+      t.end();
+    });
+  });
+  test('precedence: invalid querystring but valid header', function(t) {
+
+    var req = {
+      headers: { 'accept-language': 'fr' },
+      query: { 'lang': 'foobar' }
+    };
+
+    var expected = {
+      defaulted: false,
+      iso6391: 'fr',
+      iso6392B: 'fre',
+      iso6392T: 'fra',
+      iso6393: 'fra',
+      name: 'French',
+      scope: 'individual',
+      type: 'living'
+    };
+
+    middleware(req, {}, function () {
+      t.deepEqual( req.language, expected, '$req.language set' );
+
+      t.deepEqual( req.clean.lang, {
+        defaulted: req.language.defaulted,
+        iso6391: req.language.iso6391,
+        iso6393: req.language.iso6393,
+        name: req.language.name
+      }, '$req.clean.lang set' );
+
+      t.deepEqual( req.warnings, [
+        'invalid language provided via querystring'
+      ]);
+
+      t.end();
+    });
+  });
+};
+
+module.exports.all = function (tape, common) {
+  function test(name, testFunction) {
+    return tape('[middleware] requestLanguage: ' + name, testFunction);
+  }
+  for( var testCase in module.exports.tests ){
+    module.exports.tests[testCase](test, common);
+  }
+};
diff --git a/test/unit/run.js b/test/unit/run.js
index a16fb18e..ad358e30 100644
--- a/test/unit/run.js
+++ b/test/unit/run.js
@@ -39,6 +39,7 @@ var tests = [
   require('./middleware/normalizeParentIds'),
   require('./middleware/trimByGranularity'),
   require('./middleware/trimByGranularityStructured'),
+  require('./middleware/requestLanguage'),
   require('./query/autocomplete'),
   require('./query/autocomplete_defaults'),
   require('./query/search_defaults'),