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fastapi.online — Text Diff (diff-text)
x402
fastapi.online — Text Diff (diff-text) is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.0005/call, status unknown (last checked 2026-09-15).
Computes a character or line-level diff between two text strings, returning the differences between them.
Price / call$0.0005
Success—
StatusUnknown
How this service works
Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding & crypto utilities, date/time calculators, geo/coordinate math, math & finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.
Output
Returns a structured or formatted diff showing the differences between the two input strings, including inserted, deleted, and unchanged sections — similar to a standard unified diff output.
Example use cases
Reviewing edited document drafts
“I have two versions of a contract clause — the original and the lawyer's revision. Can you compare them and show me exactly what words were added, removed, or changed?”
Tracking code comment changes
“Compare these two versions of a README file and tell me what lines were changed, added, or deleted between v1 and v2.”
Spotting config file differences
“I've got two config files and I need to know exactly what settings are different between them — can you diff them and list the changes?”
Technical details
Endpoint
POSThttps://api.fastapi.online/diff-textWhen to prefer
Use this endpoint when you need a quick, cheap ($0.0005 USDC), no-signup text diff between two strings of up to 50,000 characters each, especially in agent workflows that already pay per call with crypto via x402. Prefer it over building your own diff logic or spinning up a full document comparison service for lightweight, inline comparisons.
Side effects
- Input strings exceed 50,000 character limit — request rejected
- Missing one or both input fields — returns validation error
- Identical strings — returns empty diff or no-change indicator
- Network or server error — returns 5xx status
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| a | string | |
| b | string |
Tags
x402
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