Text comparison API
When comparisons are frequent and part of the process, doing them by hand stops working. The API takes two texts and returns a structured result: change blocks, added and removed lines, a similarity ratio. The response is JSON, so it is easy to embed into a CI check, contract approval or export reconciliation. An active plan is required.
Supported: .conf, .css, .csv, .docx, .htm, .html, .ini, .js, .json, .log, .md, .pdf, .php, .py, .sh, .sql, .ts, .tsv, .txt, .xls, .xlsx, .xml, .yaml, .yml. Limit: 10000 lines for two documents. Nothing is stored — only a fingerprint of the pair stays on the server.
Features
- POST /api/v1/diff with an X-API-Key header
- Up to 25,000 lines per request
- JSON response: hunks, added, removed, similarity
- Rate limit of 60 requests per minute per key
- Keys are stored hashed — they cannot be recovered, only reissued
Questions and answers
How do I get an API key?
The key is issued in your account after subscribing. Only a hash is stored, so a lost key is recovered by reissuing it.
What does the API return?
JSON: an equality flag, line counts, the number of added and removed lines, a similarity ratio and a list of change blocks.
Is there a test mode?
Payments are tested in the RollyPay sandbox. For the API, a test key is issued separately on request to support.
What is the request limit?
60 requests per minute per key. Exceeding it returns 429.
Ready to start? The working screen is above. Need unlimited comparisons — see the plans.
Page updated: 2026-11-10
Related pages
- Compare code — Compare two code snippets: line-by-line changes and inline highlighting. Python, JS, PHP, SQL, CSS, HTML, JSON and other languages. For free.
- Compare two documents — Upload two documents and get a report of the differences: edits, insertions, deletions. Supports DOCX, PDF, XLSX, XLS and plain text formats.
- Compare texts with highlighted differences — Compare two texts and see differences down to the character: changed lines and highlighted fragments inside them. The first 10 pairs are free.
- Text comparison pricing — prices and terms.