LLM Response Diff Viewer

Paste two LLM responses and instantly see a colour-coded diff that highlights every addition, deletion and modification at word or sentence level. Perfect for prompt engineers who iterate on system prompts, compare model outputs, or A/B test different instructions. Choose between inline and split-view modes, switch between word-level and sentence-level granularity, attach metadata like model name and temperature, and export your comparison as HTML or plain text. Everything runs client-side — your prompts and responses never leave your browser.

Word & Sentence Diff Split & Inline View Model Metadata Tags Similarity Score HTML & Text Export

Quick Examples

PROMPT_AB: Compare Response A (GPT-4o) vs Response B (Claude Sonnet) on the same prompt
ITERATION: Diff v1 and v2 of a system prompt to see what effect your change had
MODELS: A/B test two temperature settings and highlight tone differences

Granularity

Word Sentence

Response A

Words: 0 Chars: 0

Response B

Words: 0 Chars: 0

Statistics

Added

Removed

Changes

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Similar

Original Prompt (optional reference)

Diff Result

Added Removed

							
							Paste two responses on the left, or load an example pair above.
						

Help & Related Tools

Everything you need to know

FAQ Frequently Asked Questions

What does the LLM Response Diff Viewer do?

The tool compares two AI-generated text responses and highlights every difference using colour-coded markup: green for additions, red for deletions, and yellow for modified words. It works in both split-view (side-by-side panels) and inline mode, and supports word-level or sentence-level granularity. A similarity score shows how close the two responses are overall.

How do I use the diff viewer for prompt engineering?

Paste your first model response (e.g. from GPT-4o) into the left panel and your second response (e.g. from Claude Sonnet, or the same model with a modified prompt) into the right panel. The diff updates in real time. Use the metadata fields to tag each response with its model name, prompt version, or temperature setting so you can keep track of your iterations.

What is the difference between word-level and sentence-level diff?

Word-level diff highlights individual word changes and is ideal for short responses or precise wording comparisons. Sentence-level diff groups changes by sentence, making it easier to understand structural differences in longer responses. You can switch between the two modes at any time without re-entering your text.

Is my text sent to a server when I use this tool?

No. All diffing is performed entirely in your browser using the open-source jsdiff library. No text is uploaded, stored or transmitted. This makes the tool safe to use with proprietary prompts, confidential documents, or internal system messages.

Are there any limitations on text length?

The tool handles responses up to approximately 50,000 words comfortably. Very long texts may cause a brief calculation delay on slower devices, but there is no hard character limit. All processing happens locally in the browser, so performance depends on your device rather than server capacity.