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Prompt Diff Viewer

Compare two prompts side-by-side and see exactly what changed

+5 added -4 removed 0 unchanged
Original (Left)
Modified (Right)

Diff Result

1 You are a helpful AI assistant.
2
3 Be concise and clear in your responses.
4 Always provide accurate information.
1 You are a helpful AI assistant specialized in coding.
2
3 Be concise and clear in your responses.
4 Always provide accurate information.
5 Include code examples when relevant.

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Why Compare Prompts?

When iterating on prompts, small changes can have big effects. A single word modification might dramatically improve response quality — or break something that was working. This tool helps you see exactly what changed between two prompt versions, making it easier to understand the impact of modifications and identify what's working.

Whether you're debugging a regression, documenting improvements, or reviewing a colleague's changes, seeing a visual diff makes the differences immediately obvious instead of having to read and re-read two prompts to spot what's different.

Use Cases for Prompt Diffing

🔍 Debugging

When a prompt stops working, compare it to a known good version to find what broke.

📝 Documentation

Create clear changelogs by exporting diffs as markdown for team documentation.

👥 Code Review

Review prompt changes from teammates before they go into production.

📊 A/B Analysis

Understand exactly what differs between A/B test variants to explain performance differences.

How to Use This Tool

  1. Paste the original prompt — Put your baseline or "before" version in the left textarea.
  2. Paste the modified prompt — Put your updated or "after" version in the right textarea.
  3. Review the diff — Scroll through the comparison below. Green highlights show additions; red shows deletions.
  4. Switch view modes — Use "Side by Side" for complex changes or "Unified" for simpler linear viewing.
  5. Swap if needed — Click "Swap" to reverse which prompt is considered original vs. modified.
  6. Export the diff — Click "Copy Diff" to get a markdown-formatted diff you can paste into documentation.

Understanding the Output

+ Added line

Lines that exist in the modified version but not the original.

- Removed line

Lines that existed in the original but were removed in the modified version.

  Unchanged

Lines that are identical in both versions (context).

Tips for Effective Comparison

  • Make small, focused changes — The diff is more useful when each version differs by only one or two logical changes.
  • Preserve formatting — Keep line breaks and structure consistent so the diff shows meaningful differences, not formatting noise.
  • Use with Version Tracker — Combine this tool with version tracking for a complete prompt engineering workflow.
  • Document important diffs — When you find a significant improvement, save the diff as part of your prompt changelog.

Frequently Asked Questions

What's the difference between Side by Side and Unified view?

Side by Side shows both versions in parallel columns, making it easy to see corresponding lines. Unified shows a single stream where additions and deletions are mixed together, similar to Git diff output. Side by Side is better for complex changes; Unified is more compact.

Does this tool support word-level highlighting?

Currently, the tool performs line-by-line comparison. If a line has small changes, the entire line is shown as modified. For word-level precision, compare shorter prompts or break your prompt into more lines.

Can I compare prompts from different files?

Yes! Just copy and paste content from any source. The tool works with any text — copy from files, documents, chat logs, or version control systems.

What format does "Copy Diff" use?

The copied diff uses standard markdown diff format (```diff``` code block with + for additions and - for deletions). This renders nicely in GitHub, Notion, and most documentation tools.

Related Tools

  • • Prompt Version Tracker — Track multiple versions and compare any two from history
  • • System Prompt Builder — Create well-structured prompts to compare
  • • Token Counter — Check if your changes affected token usage