// compare prompt versions side by side
Compare two prompt versions side by side and highlight exactly what changed — additions, removals, and intent shifts. Free, browser-based, no sign-up.
Diff will appear here
Paste two prompt versions above and click ComparePaste your original prompt in the left panel (Version A).
Paste the updated prompt in the right panel (Version B).
Select Word, Line, or Char granularity, then click Compare.
Green = added, red = removed. Check the similarity score and stats.
The Prompt Version Comparator highlights exactly what changed between two versions of an AI prompt — word by word, line by line, or character by character. Use it to track edits, review intent shifts, and ensure your prompt improvements are exactly what you intended.
All processing happens entirely in your browser. Your prompts are never uploaded to any server.
No. All diffing is done entirely in your browser using JavaScript. Your prompts never leave your device and are not stored anywhere.
Word mode highlights individual word changes (best for prose prompts). Line mode shows entire changed lines (best for structured prompts). Char mode highlights single character differences (best for catching typos).
It shows what percentage of the total content is shared between Version A and B. 100% means identical, 0% means completely different. It's calculated based on matching tokens in the selected diff mode.
Absolutely. The tool works with any text — system prompts, user messages, few-shot examples, chain-of-thought instructions, or raw text. There's no prompt-specific syntax required.
When enabled, the diff treats uppercase and lowercase letters as identical. "Hello" and "hello" would be considered the same. Useful when capitalisation changes are not meaningful to you.
When enabled, extra spaces, tabs, and newlines are collapsed before diffing. This means formatting-only changes won't be flagged, letting you focus on content changes.
There's no hard limit — the tool runs in your browser and can handle very long prompts. For prompts over 50,000 characters, performance may slow slightly depending on your device.
Currently the tool supports pairwise comparison (A vs B). For multi-version tracking, compare sequentially: A→B, then B→C, and so on.
A Prompt Version Comparator is a tool that highlights the differences between two versions of an AI prompt. As you iterate on system prompts, user messages, or few-shot examples, it's easy to lose track of exactly what changed — and whether those changes actually improved things. This tool gives you a visual, word-level diff so you can review every edit with precision.
Whether you're refining a GPT-4 system prompt, iterating on a Claude instruction set, or comparing two variants for an A/B test, the comparator makes the differences impossible to miss.
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Prompt engineering is iterative by nature. You start with a draft, test it, notice issues, tweak a few words, and test again. But without version tracking, these small edits accumulate invisibly. A week later, you may not remember whether you changed the tone instruction, updated the output format requirement, or removed a key constraint. The Prompt Version Comparator solves this by making changes visible and explicit.
Teams working on shared AI products face this even more acutely. When multiple engineers edit a system prompt, understanding what changed — and why — becomes critical for maintaining quality and preventing regressions.
Not all prompts benefit from the same granularity of comparison. The tool supports three diff modes to match your workflow:
The similarity percentage gives you an at-a-glance sense of how much changed between two versions. A score above 90% usually means minor polish — a few word tweaks or a sentence rewrite. A score below 50% signals a significant structural revision. A score near 0% means you're essentially comparing two completely different prompts.
This metric is especially useful when reviewing pull requests or prompt change proposals in a team setting. It contextualises the diff and helps prioritise review effort.
One powerful workflow is to use the comparator alongside A/B testing. When you test two prompt variants with an LLM, you'll often find one performs better — but you may not know exactly why. By comparing the two prompts in the comparator, you can isolate exactly what differed and form a clearer hypothesis about which specific change drove the improvement.
For example, if Prompt B outperforms Prompt A, and the diff reveals you added the phrase "think step by step" before the final instruction, you now have a hypothesis: chain-of-thought prompting improved the result. You can test this independently in the next iteration.
All processing in this tool happens entirely in your browser. Your prompts — which may contain sensitive instructions, business logic, or proprietary system designs — are never sent to any external server. The tool has no backend, no logging, and no storage. Once you close the tab, nothing persists.
This makes the Prompt Version Comparator safe to use even with confidential system prompts for internal AI products or enterprise deployments.
After comparing hundreds of prompt iterations, some change patterns are particularly worth paying attention to:
The Prompt Version Comparator makes all of these patterns immediately visible, turning what would otherwise be a manual review process into a fast, visual inspection.
Keep changes small and isolated where possible — change one thing at a time so you can attribute performance differences accurately. Use version labels or comments in your prompt files to record the rationale for each change. When a prompt regresses after an edit, use the comparator to quickly identify what changed and revert just that piece. Treat your prompts like code: version control, review, and test before deploying.