Why Captcha Tokens Fail: The IP Address Mismatch

Two requests, one visitor

From the website's side, solving the captcha and sending the form are two actions by one visitor. Some sites record the IP address that completed the captcha and compare it with the address that submits the token. If they differ, the token is treated as borrowed.

Proxyless and proxy tasks

Solving services usually offer each task in two forms. In the proxyless form the service solves from its own addresses. In the other form it solves through a proxy you give it. The second is the one that keeps both actions on one address.

Getting it right

1. Use a sticky session, so the address holds for both steps.
2. Give the service exactly the same username, including the session ID, that your own client uses.
3. Send the same User-Agent to the service that your client sends to the site.
4. Submit the token promptly. Tokens expire, usually within a couple of minutes.

The username to use in both places

USERNAME-country-us-time-600-session-a1b2c3d4

When proxyless is enough

Many sites do not compare addresses. Try the proxyless task first: it is simpler, and it uses none of your traffic. Move to the proxy form when tokens come back valid but are refused.

Guides for each service

• 2Captcha2Captcha is a long-running captcha solving service with a simple HTTP API. Its newer API takes a task as JSON, and a task can carry your own proxy.
• Anti-CaptchaAnti-Captcha is one of the oldest captcha solving services. Its JSON API has two versions of most tasks: a proxyless one, and one that works through a proxy you supply.
• CapSolverCapSolver is an automated captcha solving service with a JSON API. Tasks that need your IP address take the proxy as a single string.
• CapMonster CloudCapMonster Cloud is the hosted captcha solving service from ZennoLab. Its API follows the same task format as Anti-Captcha, so code written for one usually works with the other.
• DeathByCaptchaDeathByCaptcha is one of the older captcha solving services, with an HTTP API and client libraries for the common languages.
• CaptchaAICaptchaAI is an automated captcha solving service whose API copies the 2Captcha request format, so tools with 2Captcha support can be pointed at it.
• NopeCHANopeCHA solves captchas with a browser extension and with an API. The extension works inside your browser; the API's token requests can take a proxy.
• NextCaptchaNextCaptcha is a captcha solving API that follows the task format made common by Anti-Captcha, with proxyless tasks and tasks that use your proxy.

Questions