Prompt Diff & Version Compare
Compare two prompt versions side-by-side. See exactly what changed with token counts.
How to Use This Tool
- Paste your original prompt in the left text area and the modified version in the right text area.
- Click 'Compare' to generate the diff. Additions are highlighted in green, deletions in red.
- Switch between diff modes: Line Level (best for structural changes), Word Level (best for prompt editing), and Character Level (best for catching typos).
- Review the token count delta to understand how your changes affect API costs.
- Use the 'Share' button to generate a URL that encodes both prompts — share it with teammates for review. No data is stored on any server.
Why Prompt Versioning Matters
Prompt engineering is an iterative process. Small wording changes in a system prompt can dramatically affect the quality, tone, and accuracy of AI outputs. Without tracking what changed between versions, it's easy to lose track of which modifications improved or degraded performance.
Professional prompt engineers typically maintain version histories of their prompts, similar to how developers use git for code. This tool provides a lightweight, instant way to compare two versions side-by-side with highlighted differences and token count impact — no setup or account required.
The token count comparison is especially useful for cost-conscious teams. Adding a few-shot example to your prompt might improve accuracy but could add 500+ tokens per request. With this tool, you can see the exact token cost of each change and make informed decisions about the quality-cost tradeoff.
For teams, the shareable URL feature enables asynchronous prompt review. Encode both prompt versions in a URL, share it in Slack or email, and your team can instantly see the diff without needing any tool installed. All data stays in the URL hash — nothing is sent to any server.
Last updated: February 2026
FAQ
Why do I need a prompt diff tool?
When iterating on prompts, it's crucial to track exactly what changed between versions. Small wording changes can significantly affect LLM output. This tool highlights every difference and shows the token count impact.
What diff modes are available?
Three modes: Line-level (compare line by line), Word-level (compare word by word), and Character-level (compare character by character). Word-level is usually the most useful for prompt comparison.
Can I share a diff?
Yes! Click 'Share' to generate a URL that encodes both prompts. Send the URL to a colleague and they'll see the same diff. All data is encoded in the URL hash — nothing is stored on any server.
How does the share URL work?
When you click 'Share', both prompt versions are encoded into the URL's hash fragment (the part after #). This means the data never leaves your browser or touches any server. Anyone with the URL can see the same diff instantly. URLs are safe to share via Slack, email, or any messaging platform.
Can I use this for comparing code or other text?
Yes! While this tool is optimized for prompt comparison (with token counting), it works for any text comparison. You can use it to diff code snippets, configuration files, or any two text versions. The word-level and character-level modes are especially useful for detailed text comparison.