SVG captchas
2026-01-22 · Captchas
Some portals draw the captcha as SVG. The service renders it locally and does not fetch anything the file points at.
An SVG captcha is markup, not pixels. The solver renders it, then reads the picture. Rendering stops at 1200 pixels, and the SVG is not allowed to load a file or a URL. That blocks a document that tries to pull in a remote image.
Send the SVG text as the image string, base64-encoded, the same way you send a PNG. If the string is longer than 7 million characters the request is a 422.
A broken SVG comes back as invalid_image and is free. Do not wrap the SVG in an HTML page. Send the <svg> document itself.
PNG is still the better choice when the portal offers both. You already have the pixels, and there is no render step.
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