# Prompt Diff Checker

> Paste two versions of a prompt and see every word added or removed, highlighted, with word counts and the token change. Free, runs in your browser.

Canonical: https://promptitin.com/free-tools/prompt-diff-checker
Last updated: 2026-11-13

Changed a prompt and the answers changed too? Paste both versions to see exactly which words moved, so you know what made the difference.

This is an interactive tool. Use it at https://promptitin.com/free-tools/prompt-diff-checker.

## How to use it

1. Paste the old prompt on the left and the new one on the right, or tap Try an example.
2. Pick Words for small edits, or Lines for long prompts.
3. Read the changes: red was removed, green was added.

## Tips

- Change one thing at a time when testing prompts. A diff makes it easy to check you did.
- Watch the token count. A small edit can add a lot of tokens, and cost, at scale.
- Keep each version you test, with a note on what it did better.
- Use Lines mode for system prompts and long templates.

## FAQ

### What is a prompt diff?

A side-by-side comparison that shows exactly what changed between two versions of a prompt, word by word or line by line.

### Does it work for any text?

Yes. Prompts, emails, code or any two texts.

### How are tokens counted?

As an estimate of about 4 characters per token for English, close to what most models use. Exact counts differ a little between models.

### Is my text sent anywhere?

No. The comparison runs in your browser.

## Related

- [Prompt Grader](https://promptitin.com/free-tools/prompt-grader)
- [AI Token Counter](https://promptitin.com/free-tools/ai-token-counter)
- [Prompt Variable Filler](https://promptitin.com/free-tools/prompt-variable-filler)
- [Few-Shot Prompt Formatter](https://promptitin.com/free-tools/few-shot-prompt-formatter)