A short glossary
2026-05-07 · Captchas
The words the API uses, in one place, so the rest of the guides stay short.
Image is the base64 file. Text is what you type into the portal. Reliable means you were charged and you should submit. Expression is the sum the math engines saw. Raw is the characters before the computed answer.
Engine is ocr, math, or hindi_math. Credit is one reliable answer. Task id is the integer you report later. Key is the bearer secret.
422 means fix the JSON. 402 means buy credits. 401 means fix the key. 429 means slow down. 503 means retry later. A 200 with error means the image was free and bad.
The guides index links the longer notes. The API reference is the field list.
Ready to call it? Start with the quickstart, the API guide, or pricing.