UPDATE

The Google Translate API has been officially deprecated  an alternative  is the Microsoft Translator V2, check this article for more details.

In this past post we use the Google translate API v2 to translate from an language to another. today will show how use the current version of this API (v1) which include a nice functionality to detect the language from a given text.

This API can be accessed via JavaScript  in a web page or using a HTTP request. in the next sample i will use the second option.

Before to continue you must aware of this warning of Google.

Note: The Google Translate API must be used for user-generated translations. Automated or batched queries of any kind are strictly prohibited.

Here you can find the Terms of Service of this API.

The next code is for educational purposes only.

To detect the language from a text you must make  a request to his URI

https://ajax.googleapis.com/ajax/services/language/detect?v=1.0&q=Hello+World

As you can see the only required parameter is the encoded text to detect.

the  JSON response to this request will be something like this

{ "responseData" : { "confidence" : 0.11489271400000001,
      "isReliable" : false,
      "language" : "en"
    },
  "responseDetails" : null,
  "responseStatus" : 200
}

the responseStatus contain the result of the operation, the 200 indicate which the language from text was successfully detected.

So now we need to define a few types, functions and constants to make the work more easy.

type
  //the supported languages
  TGoogleLanguages=
  (Autodetect,Afrikaans,Albanian,Arabic,Basque,Belarusian,Bulgarian,Catalan,Chinese,Chinese_Traditional,
  Croatian,Czech,Danish,Dutch,English,Estonian,Filipino,Finnish,French,Galician,German,Greek,
  Haitian_Creole,Hebrew,Hindi,Hungarian,Icelandic,Indonesian,Irish,Italian,Japanese,Latvian,
  Lithuanian,Macedonian,Malay,Maltese,Norwegian,Persian,Polish,Portuguese,Romanian,Russian,
  Serbian,Slovak,Slovenian,Spanish,Swahili,Swedish,Thai,Turkish,Ukrainian,Vietnamese,Welsh,Yiddish,Unknow);

  //the string representation for the enumerated types
  const
  GoogleLanguagesStr : array[TGoogleLanguages] of string =
  ('Autodetect','Afrikaans','Albanian','Arabic','Basque','Belarusian','Bulgarian','Catalan','Chinese','Chinese_Traditional',
  'Croatian','Czech','Danish','Dutch','English','Estonian','Filipino','Finnish','French','Galician','German','Greek',
  'Haitian_Creole','Hebrew','Hindi','Hungarian','Icelandic','Indonesian','Irish','Italian','Japanese','Latvian',
  'Lithuanian','Macedonian','Malay','Maltese','Norwegian','Persian','Polish','Portuguese','Romanian','Russian',
  'Serbian','Slovak','Slovenian','Spanish','Swahili','Swedish','Thai','Turkish','Ukrainian','Vietnamese','Welsh','Yiddish','Unknow');

  //The languages code to be used in HTTP request
  GoogleLanguagesArr : array[TGoogleLanguages] of string =
  ( 'Autodetect','af','sq','ar','eu','be','bg','ca','zh-CN','zh-TW','hr','cs','da','nl','en','et','tl','fi','fr','gl',
    'de','el','ht','iw','hi','hu','is','id','ga','it','ja','lv','lt','mk','ms','mt','no','fa','pl','pt',
    'ro','ru','sr','sk','sl','es','sw','sv','th','tr','uk','vi','cy','yi','Unknow');

  //URI to translate a text using the V1 from the API
  GoogleTranslateUrl='https://ajax.googleapis.com/ajax/services/language/translate?v=1.0&q=%s&langpair=%s';
  //URI to detect the language from a text
  GoogleLngDetectUrl='https://ajax.googleapis.com/ajax/services/language/detect?v=1.0&q=%s';

//return a stream containing the HTTP response InternetOpen
procedure WinInet_HttpGet(const Url: string;Stream:TStream);overload;
const
BuffSize = 1024*1024;
var
  hInter   : HINTERNET;
  UrlHandle: HINTERNET;
  BytesRead: DWORD;
  Buffer   : Pointer;
begin
  hInter := InternetOpen('', INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
  if Assigned(hInter) then
  begin
    Stream.Seek(0,0);
    GetMem(Buffer,BuffSize);
    try
        UrlHandle := InternetOpenUrl(hInter, PChar(Url), nil, 0, INTERNET_FLAG_RELOAD, 0);
        if Assigned(UrlHandle) then
        begin
          repeat
            InternetReadFile(UrlHandle, Buffer, BuffSize, BytesRead);
            if BytesRead>0 then
             Stream.WriteBuffer(Buffer^,BytesRead);
          until BytesRead = 0;
          InternetCloseHandle(UrlHandle);
        end;
    finally
      FreeMem(Buffer);
    end;
    InternetCloseHandle(hInter);
  end
end;

//return a string containing the HTTP response.
function WinInet_HttpGet(const Url: string): string;overload;
Var
  StringStream : TStringStream;
begin
  Result:='';
    StringStream:=TStringStream.Create('',TEncoding.UTF8);
    try
        WinInet_HttpGet(Url,StringStream);
        if StringStream.Size>0 then
        begin
          StringStream.Seek(0,0);
          Result:=StringStream.ReadString(StringStream.Size);
        end;
    finally
      StringStream.Free;
    end;
end;

And now to process the response using the DBXJSON unit

function DetectLanguage_DBXJSON(const Text:string):TGoogleLanguages;
var
  EncodedRequest: string;
  json          : TJSONObject;
  jPair         : TJSONPair;
  jValue        : TJSONValue;
  Response      : string;
  Lng           : TGoogleLanguages;
  LngStr        : string;
begin
  Result:=Unknow;
  EncodedRequest:=Format(GoogleLngDetectUrl,[HTTPEncode(Text)]);
  Response:=WinInet_HttpGet(EncodedRequest);

  if Response<>'' then
  begin
      json    := TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(Response),0) as TJSONObject;
    try
      jPair   := json.Get(2);//get the responseStatus
      if jPair.JsonValue.ToString<>'200' then  //200 is all ok
        Result := Unknow
      else
      begin
        jPair  := json.Get(0);
        jValue := TJSONObject(jPair.JsonValue).Get(0).JsonValue;
        LngStr := jValue.Value;
        for lng:=Low(TGoogleLanguages) to High(TGoogleLanguages)  do
        if GoogleLanguagesArr[Lng]=LngStr then
        begin
         Result:=lng;
         exit;
        end;
      end;
    finally
       json.Free;
    end;
  end;
end;

Another alternative using the JSON superobject library

function DetectLanguage_JSONsuperobject(const Text:string):TGoogleLanguages;
var
  EncodedRequest: string;
  Response      : string;
  Lng           : TGoogleLanguages;
  LngStr        : string;
begin
  Result:=Unknow;
  EncodedRequest:=Format(GoogleLngDetectUrl,[HTTPEncode(Text)]);
  Response:=WinInet_HttpGet(EncodedRequest);
  if Response<>'' then
  begin
    if SO(Response)['responseStatus'].AsInteger<>200 then   //if responseStatus<>200 then exist a error in the response
      Result:=Unknow
    else
    begin
      LngStr:=SO(Response)['responseData.language'].AsString;
      for lng:=Low(TGoogleLanguages) to High(TGoogleLanguages)  do
      if GoogleLanguagesArr[Lng]=LngStr then
      begin
       Result:=lng;
       exit;
      end;
    end;
  end;
end;

and finally a option without JSON

function DetectLanguage_JSONLess(const Text:string):TGoogleLanguages;
const
  TagErr='{"responseData": null,';
  TagIOk='{"responseData": {"language":"';
  TagFOk='","isReliable":';
var
  EncodedRequest: string;
  Response      : string;
  Lng           : TGoogleLanguages;
  LngStr        : string;
begin
  Result:=Unknow;
  EncodedRequest:=Format(GoogleLngDetectUrl,[HTTPEncode(Text)]);
  Response:=WinInet_HttpGet(EncodedRequest);

  if Response<>'' then
  begin
    if StartsStr(TagErr,(Response)) then  //Response  Error
    begin
      Result:=Unknow
    end
    else
    begin  //Response Ok
      LngStr:=StringReplace(Response,TagIOk,'',[rfReplaceAll]);
      LngStr:=Copy(LngStr,1,Pos(TagFOk,LngStr)-1);
        for lng:=Low(TGoogleLanguages) to High(TGoogleLanguages)  do
        if GoogleLanguagesArr[Lng]=LngStr then
        begin
         Result:=lng;
         exit;
        end;
    end;
  end;
end;

To finish here i leave the full source code from a console application which show all the alternatives to decode the JSON response and as extra include the routine to translate a text using the Google translate API v1.

program GoogleAPITranslateV1;

{$APPTYPE CONSOLE}
{$DEFINE USE_SUPER_OBJECT}
{$DEFINE USE_DBXJSON}
{$DEFINE USE_JSONLess}

uses
  Windows
  ,Classes
  ,WinInet
  ,Activex
  ,HTTPApp
  ,SysUtils
  {$IFDEF USE_JSONLess}
  ,StrUtils
  {$ENDIF}
  {$IFDEF USE_SUPER_OBJECT}
  ,superobject
  {$ENDIF}
  {$IFDEF USE_DBXJSON}
  ,DBXJSON
  {$ENDIF}
  ;

type
  TGoogleLanguages=
  (Autodetect,Afrikaans,Albanian,Arabic,Basque,Belarusian,Bulgarian,Catalan,Chinese,Chinese_Traditional,
  Croatian,Czech,Danish,Dutch,English,Estonian,Filipino,Finnish,French,Galician,German,Greek,
  Haitian_Creole,Hebrew,Hindi,Hungarian,Icelandic,Indonesian,Irish,Italian,Japanese,Latvian,
  Lithuanian,Macedonian,Malay,Maltese,Norwegian,Persian,Polish,Portuguese,Romanian,Russian,
  Serbian,Slovak,Slovenian,Spanish,Swahili,Swedish,Thai,Turkish,Ukrainian,Vietnamese,Welsh,Yiddish,Unknow);

  const
  GoogleLanguagesStr : array[TGoogleLanguages] of string =
  ('Autodetect','Afrikaans','Albanian','Arabic','Basque','Belarusian','Bulgarian','Catalan','Chinese','Chinese_Traditional',
  'Croatian','Czech','Danish','Dutch','English','Estonian','Filipino','Finnish','French','Galician','German','Greek',
  'Haitian_Creole','Hebrew','Hindi','Hungarian','Icelandic','Indonesian','Irish','Italian','Japanese','Latvian',
  'Lithuanian','Macedonian','Malay','Maltese','Norwegian','Persian','Polish','Portuguese','Romanian','Russian',
  'Serbian','Slovak','Slovenian','Spanish','Swahili','Swedish','Thai','Turkish','Ukrainian','Vietnamese','Welsh','Yiddish','Unknow');

  GoogleLanguagesArr : array[TGoogleLanguages] of string =
  ( 'Autodetect','af','sq','ar','eu','be','bg','ca','zh-CN','zh-TW','hr','cs','da','nl','en','et','tl','fi','fr','gl',
    'de','el','ht','iw','hi','hu','is','id','ga','it','ja','lv','lt','mk','ms','mt','no','fa','pl','pt',
    'ro','ru','sr','sk','sl','es','sw','sv','th','tr','uk','vi','cy','yi','Unknow');

  GoogleTranslateUrl='https://ajax.googleapis.com/ajax/services/language/translate?v=1.0&q=%s&langpair=%s';
  //http://code.google.com/apis/language/translate/v1/using_rest_translate.html
  GoogleLngDetectUrl='https://ajax.googleapis.com/ajax/services/language/detect?v=1.0&q=%s';

procedure WinInet_HttpGet(const Url: string;Stream:TStream);overload;
const
BuffSize = 1024*1024;
var
  hInter   : HINTERNET;
  UrlHandle: HINTERNET;
  BytesRead: DWORD;
  Buffer   : Pointer;
begin
  hInter := InternetOpen('Mozilla/3.0', INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
  if Assigned(hInter) then
  begin
    Stream.Seek(0,0);
    GetMem(Buffer,BuffSize);
    try
        UrlHandle := InternetOpenUrl(hInter, PChar(Url), nil, 0, INTERNET_FLAG_RELOAD, 0);
        if Assigned(UrlHandle) then
        begin
          repeat
            InternetReadFile(UrlHandle, Buffer, BuffSize, BytesRead);
            if BytesRead>0 then
             Stream.WriteBuffer(Buffer^,BytesRead);
          until BytesRead = 0;
          InternetCloseHandle(UrlHandle);
        end;
    finally
      FreeMem(Buffer);
    end;
    InternetCloseHandle(hInter);
  end
end;

function WinInet_HttpGet(const Url: string): string;overload;
Var
  StringStream : TStringStream;
begin
  Result:='';
    StringStream:=TStringStream.Create('',TEncoding.UTF8);
    try
        WinInet_HttpGet(Url,StringStream);
        if StringStream.Size>0 then
        begin
          StringStream.Seek(0,0);
          Result:=StringStream.ReadString(StringStream.Size);
        end;
    finally
      StringStream.Free;
    end;
end;

{$IFDEF USE_SUPER_OBJECT}
function DetectLanguage_JSONsuperobject(const Text:string):TGoogleLanguages;
var
  EncodedRequest: string;
  Response      : string;
  Lng           : TGoogleLanguages;
  LngStr        : string;
begin
  Result:=Unknow;
  EncodedRequest:=Format(GoogleLngDetectUrl,[HTTPEncode(Text)]);
  Response:=WinInet_HttpGet(EncodedRequest);
  if Response<>'' then
  begin
    if SO(Response)['responseStatus'].AsInteger<>200 then   //if responseStatus<>200 then exist a error in the response
      Result:=Unknow
    else
    begin
      LngStr:=SO(Response)['responseData.language'].AsString;
      for lng:=Low(TGoogleLanguages) to High(TGoogleLanguages)  do
      if GoogleLanguagesArr[Lng]=LngStr then
      begin
       Result:=lng;
       exit;
      end;
    end;
  end;
end;

function Translate_JSONsuperobject(const Text:string;Source,Dest:TGoogleLanguages):string;
var
  EncodedRequest: string;
  Response      : string;
begin
  Result:='';
  if Source=Autodetect then
   EncodedRequest:=Format(GoogleTranslateUrl,[HTTPEncode(Text),'%7C'+GoogleLanguagesArr[Dest]])
  else
   EncodedRequest:=Format(GoogleTranslateUrl,[HTTPEncode(Text),GoogleLanguagesArr[Source]+'%7C'+GoogleLanguagesArr[Dest]]);

  Response:=WinInet_HttpGet(EncodedRequest);
  if Response<>'' then
  begin
    if SO(Response)['responseData'].AsObject=nil then   //if the first element is null then ocurrs an error
      Result:=Format('Error Code %d %s',[SO(Response)['responseStatus'].AsInteger,SO(Response)['responseDetails'].AsString])
    else
      Result:=SO(Response)['responseData.translatedText'].AsString;
  end;
end;
{$ENDIF}

{$IFDEF USE_DBXJSON}
function DetectLanguage_DBXJSON(const Text:string):TGoogleLanguages;
var
  EncodedRequest: string;
  json          : TJSONObject;
  jPair         : TJSONPair;
  jValue        : TJSONValue;
  Response      : string;
  Lng           : TGoogleLanguages;
  LngStr        : string;
begin
  Result:=Unknow;
  EncodedRequest:=Format(GoogleLngDetectUrl,[HTTPEncode(Text)]);
  Response:=WinInet_HttpGet(EncodedRequest);
  if Response<>'' then
  begin
      json    := TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(Response),0) as TJSONObject;
    try
      jPair   := json.Get(2);//get the responseStatus
      if jPair.JsonValue.ToString<>'200' then  //200 is all ok
        Result := Unknow
      else
      begin
        jPair  := json.Get(0);
        jValue := TJSONObject(jPair.JsonValue).Get(0).JsonValue;
        LngStr := jValue.Value;
        for lng:=Low(TGoogleLanguages) to High(TGoogleLanguages)  do
        if GoogleLanguagesArr[Lng]=LngStr then
        begin
         Result:=lng;
         exit;
        end;
      end;
    finally
       json.Free;
    end;
  end;
end;

function Translate_DBXJSON(const Text:string;Source,Dest:TGoogleLanguages):string;
var
  EncodedRequest: string;
  json          : TJSONObject;
  jPair         : TJSONPair;
  jValue        : TJSONValue;
  Response      : string;
begin
  Result:='';
  if Source=Autodetect then
   EncodedRequest:=Format(GoogleTranslateUrl,[HTTPEncode(Text),'%7C'+GoogleLanguagesArr[Dest]])
  else
   EncodedRequest:=Format(GoogleTranslateUrl,[HTTPEncode(Text),GoogleLanguagesArr[Source]+'%7C'+GoogleLanguagesArr[Dest]]);

  Response:=WinInet_HttpGet(EncodedRequest);
  if Response<>'' then
  begin
      json    := TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(Response),0) as TJSONObject;
    try
      jPair   := json.Get(2);//get the responseStatus
      if jPair.JsonValue.ToString<>'200' then  //200 is all ok
        //{"responseData": null, "responseDetails": "invalid translation language pair", "responseStatus": 400}
        Result := Format('Error Code %s message %s',[json.Get(2).JsonValue.ToString,json.Get(1).JsonValue.ToString])
      else
      begin
        jPair  := json.Get(0);
        jValue := TJSONObject(jPair.JsonValue).Get(0).JsonValue;
        Result := jValue.ToString;
      end;
    finally
       json.Free;
    end;
      Result:=HTMLDecode(Result);
  end;
end;
{$ENDIF}

{$IFDEF USE_JSONLess}
function DetectLanguage_JSONLess(const Text:string):TGoogleLanguages;
const
  TagErr='{"responseData": null,';
  TagIOk='{"responseData": {"language":"';
  TagFOk='","isReliable":';
var
  EncodedRequest: string;
  Response      : string;
  Lng           : TGoogleLanguages;
  LngStr        : string;
begin
  Result:=Unknow;
  EncodedRequest:=Format(GoogleLngDetectUrl,[HTTPEncode(Text)]);
  Response:=WinInet_HttpGet(EncodedRequest); //{"responseData": {"language":"en","isReliable":false,"confidence":0.114892714},"responseDetails": null, "responseStatus": 200}

  if Response<>'' then
  begin
    if StartsStr(TagErr,(Response)) then  //Response  Error
    begin
      Result:=Unknow
    end
    else
    begin  //Response Ok
      LngStr:=StringReplace(Response,TagIOk,'',[rfReplaceAll]);
      LngStr:=Copy(LngStr,1,Pos(TagFOk,LngStr)-1);
        for lng:=Low(TGoogleLanguages) to High(TGoogleLanguages)  do
        if GoogleLanguagesArr[Lng]=LngStr then
        begin
         Result:=lng;
         exit;
        end;
    end;
  end;
end;

function Translate_JSONLess(const Text:string;Source,Dest:TGoogleLanguages):string;
const
  TagErr='{"responseData": null,';

  TagIOk='{"responseData": {"translatedText":"';
  TagAut=',"detectedSourceLanguage":"';

  TagFOk='"}, "responseDetails":';
var
  EncodedRequest: string;
  Response      : string;
begin
  Result:='';
  if Source=Autodetect then
   EncodedRequest:=Format(GoogleTranslateUrl,[HTTPEncode(Text),'%7C'+GoogleLanguagesArr[Dest]])
  else
   EncodedRequest:=Format(GoogleTranslateUrl,[HTTPEncode(Text),GoogleLanguagesArr[Source]+'%7C'+GoogleLanguagesArr[Dest]]);

  Response:=WinInet_HttpGet(EncodedRequest);
  if Response<>'' then
  begin
    if StartsStr(TagErr,(Response)) then  //Response  Error
    begin
      Result:='Error'
    end
    else
    begin  //Response Ok
      if Source=Autodetect then
      begin
        Result:=StringReplace(Response,TagIOk,'',[rfReplaceAll]);
        Result:=Copy(Result,1,Pos(TagAut,Result)-2);
      end
      else
      begin
        Result:=StringReplace(Response,TagIOk,'',[rfReplaceAll]);
        Result:=Copy(Result,1,Pos(TagFOk,Result)-1);
      end;
    end;

    Result:=HTMLDecode(Result);
  end;
end;
{$ENDIF}

Const
 Text   ='Hello World';
 TextEn ='Hello World';
 TextEs ='Hola Mundo';
Var
 TranslatedText : string;
begin
  try
    CoInitialize(nil);
    try
       {$IFDEF USE_JSONLess}
       Writeln('Without JSON (very ugly)');
       Writeln('');
       TranslatedText:=Translate_JSONLess(Text,Autodetect,Spanish);
       Writeln(TranslatedText);
       TranslatedText:=Translate_JSONLess(Text,English,Chinese_Traditional);
       Writeln(TranslatedText);
       TranslatedText:=Translate_JSONLess(Text,English,German);
       Writeln(TranslatedText);
       TranslatedText:=Translate_JSONLess(Text,English,Danish);
       Writeln(TranslatedText);
       TranslatedText:=Translate_JSONLess(Text,English,Portuguese);
       Writeln(TranslatedText);
       Writeln('');

       Writeln('Detecting language Without JSON');
       Writeln('');
       Writeln(Format('language detected for "%s"  : %s',[TextEn,GoogleLanguagesStr[DetectLanguage_JSONLess(TextEn)]]));
       Writeln(Format('language detected for "%s"  : %s',[TextEs,GoogleLanguagesStr[DetectLanguage_JSONLess(TextEs)]]));
       {$ENDIF}

       {$IFDEF USE_SUPER_OBJECT}
       Writeln('Using the superobject library');
       Writeln('');
       TranslatedText:=Translate_JSONsuperobject(Text,Autodetect,Spanish);
       Writeln(TranslatedText);
       TranslatedText:=Translate_JSONsuperobject(Text,English,Chinese_Traditional);
       Writeln(TranslatedText);
       TranslatedText:=Translate_JSONsuperobject(Text,English,German);
       Writeln(TranslatedText);
       TranslatedText:=Translate_JSONsuperobject(Text,English,Danish);
       Writeln(TranslatedText);
       TranslatedText:=Translate_JSONsuperobject(Text,English,Portuguese);
       Writeln(TranslatedText);
       Writeln('');

       Writeln('Detecting language using the superobject library');
       Writeln('');
       Writeln(Format('language detected for "%s"  : %s',[TextEn,GoogleLanguagesStr[DetectLanguage_JSONsuperobject(TextEn)]]));
       Writeln(Format('language detected for "%s"  : %s',[TextEs,GoogleLanguagesStr[DetectLanguage_JSONsuperobject(TextEs)]]));
       {$ENDIF}

       {$IFDEF USE_DBXJSON}
       Writeln('Using the DBXJSON unit');
       Writeln('');
       TranslatedText:=Translate_DBXJSON(Text,Autodetect,Spanish);
       Writeln(TranslatedText);
       TranslatedText:=Translate_DBXJSON(Text,English,Chinese_Traditional);
       Writeln(TranslatedText);
       TranslatedText:=Translate_DBXJSON(Text,English,German);
       Writeln(TranslatedText);
       TranslatedText:=Translate_DBXJSON(Text,English,Danish);
       Writeln(TranslatedText);
       TranslatedText:=Translate_DBXJSON(Text,English,Portuguese);
       Writeln(TranslatedText);
       Writeln('');

       Writeln('Detecting language using the DBXJSON unit');
       Writeln('');
       Writeln(Format('language detected for "%s"  : %s',[TextEn,GoogleLanguagesStr[DetectLanguage_DBXJSON(TextEn)]]));
       Writeln(Format('language detected for "%s"  : %s',[TextEs,GoogleLanguagesStr[DetectLanguage_DBXJSON(TextEs)]]));
       {$ENDIF}

    finally
     CoUninitialize;
    end;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  Readln;
end.