Really Simple CAPTCHA

Really Simple CAPTCHA is a CAPTCHA module intended to be called up from other plugin. It was originally created for my Contact Form 7 plugin, and is now an independent, stand-alone plugin.

If you are a WordPress plugin developer and are considering putting a simple CAPTCHA into your plugin, this would be a good choice.

Download | Support Forum

Click here to lend your support to: Support Really Simple CAPTCHA plugin for WordPress and make a donation at !

A Note for Contact Form 7 Users

Note: You will need this Really Simple CAPTCHA plugin installed on WordPress if you use CAPTCHA with the next (Version 1.9.4) and subsequent releases of Contact Form 7. If you don’t use CAPTCHA, you don’t have to do so.

The key reason why I’ve separated the CAPTCHA module out is to solve current problems related to the automatic upgrading of the plugin; I often receive trouble reports of failed automatic upgrades from Contact Form 7 users.

I’m guessing that the cause of the problem is in the CAPTCHA module itself. The CAPTCHA module includes font files which are relatively large binary files. It doesn’t normally cause any difficulty on most hosts; however, in some specific environments it is possible that they may cause problems.

To reduce the risk of failing automatic upgrades of Contact Form 7, I have extracted the CAPTCHA module to stand as an independent plugin. As the frequency of updating the CAPTCHA module is much less than the frequency of updating Contact Form 7, it will be less frustrating for you, even if you continue to have trouble when you upgrade the CAPCHA module.


See also: Tips for troubleshooting Really Simple Captcha issues


Really Simple CAPTCHA は別のプラグインからコールされることを意図して作られた CAPTCHA のモジュールです。元は Contact Form 7 用に作ったモジュールですがこの度スタンドアロンのプラグインとして独立させました。

もしあなたがプラグインの開発者で、自分のプラグインに簡単な CAPTCHA 機能を組み込みたいなら、これを使うと便利かもしれません。

Contact Form 7 をお使いの方へ

お知らせ: 次期バージョン (1.9.4) 以降の Contact Form 7 で CAPTCHA を使用する場合にはこの Really Simple CAPTCHA プラグインのインストールが別途必要になります。CAPTCHA を使用しない場合は必要ありません。

現在、Contact Form 7 のユーザーから「プラグインの自動アップグレードに失敗する」という報告を頻繁に頂いています。CAPTCHA モジュールを分離したことの隠れた真の理由はこれの解決にあります。

自動アップグレードに失敗する原因のひとつとして考えられるのは、CAPTCHA モジュールで同梱使用しているフォントファイルが大きすぎることです。たいていのホストでは問題なく処理できる大きさではあるのですが、一部の環境で問題を生じる可能性は否定できません。

Contact Form 7 の自動アップグレード時の失敗リスクを軽減するために、CAPTCHA モジュールをパッケージの外に出すことにしました。CAPTCHA モジュールを更新する頻度は Contact Form 7 を更新する頻度と比べてずっと低いですので、あるいは今後も CAPCHA モジュールのアップグレード時につまづくことがあるかもしれませんが、それでも今よりイライラの回数は減るはずです。


  • CAPTCHA が機能しません。画像が表示されないのです。

    Really Simple CAPTCHA は GD および FreeType ライブラリを必要とします。それらがサーバーにインストールされていることをサーバー管理者にお問い合わせください。

    それから、一時ファイルが置かれるフォルダが書き込み可能になっていることを確認してください。一時ファイルのフォルダの位置は ReallySimpleCaptcha クラスの tmp_dir インスタンス変数の値で指定されます。この設定は呼び出し側のプラグインの設定により異なるので注意してください。例えば Contact Form 7 は通常 wp-contents/uploads/wpcf7_captcha を一時フォルダに使いますが、WordPress の設定によっては別のフォルダが使われます。

180 thoughts on “Really Simple CAPTCHA

  1. Ok I’ve solved it, strange phenomenon though.

    I modified these rules (in really-simple-captcha.php)

    $this->bg = array( 255, 255, 255 );
    $this->fg = array( 0, 0, 0 );

    (which shows as a black png)


    $this->bg = array( 255, 255, 255 );
    $this->fg = array( 255, 0, 0 );

    Now I can see the characters again: red text on a black background eventough the bg-var says white…


  2. I installed the latest Contact Form 7 as well as the latest Really Simple CAPTCHA (both from the plugin installed in WP 2.9) and everything works until I try to submit a test form. Even though I can verify the CAPTCHA I am entering is what is being displayed, the system tells me it is wrong.

    I have tried upper-case as well as lower-case characters and nothing is working. Are cap characters required or would lower-case work?

    Not seeing anything of the recent forums stating these same issues, suggestions?

  3. When I install the Really Simple Captcha on the latest WP I get an error message which says:

    Call to undefined function imagettftext() in /home/xxxxxxxx/public_html/wp-content/plugins/really-simple-captcha/really-simple-captcha.php on line 103

    Anyone any idea what this might mean.


  4. Hello,
    I use CF7 latest release with WP 2.8.6.
    Today I installed RS Captcha but nothing happen.
    It doesn’t show captcha next the only form on my site.
    Probably I didn’t get how it works but gd and freestyle libraries are installed on Gator’s server and default dir is wp-content/uploads/wpsc (775).
    Any help is much appreciated.

  5. I have the same problem as Dan and Spencer – when the form is submitted the validation rejects the captcha code entered even though it clearly matches (tried both uppercase/lowercase) the generated captcha code. I’ve just checked the wpcf7_captcha folder and it also appears that the *.png images generated are not being cleared.

    I’m running the latest version of WordPress (2.9.1) Contact Form 7 ( and Really Simply Captcha 1.1.

    Has anyone found a solution to this yet? Its driving me mad….

  6. Thank you for the great plugins! I am running Support Tickets and Really Simple Captcha. The Captcha works with Contact Form 7 but not Support Tickets. I believe this is because of the temp directory for the image and php file. What is the temp directory I should use for Really Simple Captcha on Support Tickets?

  7. This is such a fantastic plugin that has saved me a lot of admin time, definetely recommend it to everyone on WP.

  8. Captcha was showing in upper case but only accepting lowercase letters. Something appeared wrong.

    I adjusted script…
    to force uppercase on both when checked, now read:

    function check( $prefix, $response ) {


  9. Hi, great plugin, ive just installed it on my site.

    Im a coding noob so asking for help, how can I change the width of the message box? It overlaps the edge of my sidebar.



  10. Hello

    I have a very interesting question. Do this plug-in support a gd font to be used, instead of true-type font? Any suggestions?

    Don’t tell me that my hosting provider needs to install true type font support or so help me I will slap you :)

  11. Hi,

    How do I apply some CSS, so I can place the picture?

    For now it’s hoovering compared to the input-field…

    Regards from Denmark
    \ Jean

    Btw; @tammy (July 12, 2010 at 6:47 pm)
    Yep, it works just fine ;)

  12. Hi Takayuki,

    Just a quick message to say thank you for the work. I installed it with Contact Form 7 and it was the easiest thing to do. Much easier and quicker to setup than Cforms II. Awesome!

  13. Is there something available for the visually impaired? We’d like the option for our users to hear a sound byte as an alternative.

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