Resource
Agent Regression Test Prompt
Make sure a fix didn't break three other things — compare an agent's outputs across two versions on the same scenarios and flag every behavior that changed for the worse.
Prompt Utilities
AI Text Diff Checker
Paste two texts and see exactly what changed — a git-style colored diff with additions in green, deletions in red, and word-level edits highlighted inline. It shows the mechanical difference and nothing else: no score, no verdict, no "which is better." For what a prompt revision means there's the Prompt Version Diff; for which prompt wins there's the Prompt Comparator.
Diff View
Resource
Compare Two AI Outputs
Run a prompt twice, or on two models, and diff the answers to see exactly where they differ — mechanically, without ranking them.
Resource
Compare Two Document Versions
Two versions of a document, compared line by line — which sections were added, removed, or reordered, at a glance.
Resource
Compare Two Generated Drafts
Generated two variants of a headline or a line of copy? Diff them to see precisely which words changed between the drafts.
Resource
Compare Two Texts
Drop two pieces of text side by side and get the literal difference between them — what was added, removed, and reworded.
Resource
Detect Changes Between Two Texts
Did anything change, and what exactly? Detect every change between two versions — a swapped number, an added word — with nothing missed.
Resource
Find the Differences Between Two Texts
The changes you would miss on a re-read — an added word, a swapped term — surfaced exactly, so nothing slips past.
Resource
Line-by-Line Text Diff
Compare two blocks line by line — config, lists, or records — to see exactly which lines were added, removed, or changed.
Resource
Online Diff Checker
A free, browser-based diff tool: paste two texts, get a colored diff and a change count. Nothing installed, nothing uploaded.
Resource
Text Diff Checker
Paste two texts and see exactly what changed — a git-style colored diff with additions, deletions, and word-level edits, and a mechanical change count.
Resource
Word-by-Word Text Diff
When the edits are inside a sentence, line mode is too coarse. Word mode highlights the exact words inserted and deleted.
Workflow
AI Code Refactoring Workflow
Restructure code you own without breaking it — change only what's worth changing, and prove with tests and a diff that behavior held.
Workflow
AI Agent Evaluation Workflow
Find out whether an AI agent behaves before users do — define what correct means, build test scenarios with expected outputs, catch failures and hallucinations, then regression-test each version.
Workflow
AI Reliable JSON Output Workflow
Make any AI task return JSON your code can rely on — define the schema, force the model to it, validate every response, and diff the drift when a model update breaks the shape.
How it works
Paste the original text in the first box and the changed text in the second, then pick a diff mode. The Diff Engine compares them with an LCS algorithm: Line mode treats each line as a unit (added, removed, or unchanged); Word mode highlights the exact words inserted and deleted inside changed regions; Mixed mode (the default) does both — line-level structure with word-level highlighting inside similar line pairs. Click Compare Texts for a git-style colored diff: additions in green, deletions in red, word-level edits marked inline, with a mechanical Change Summary — N lines added, removed, changed, and N words inserted and deleted. The copyable report breaks it into Added, Removed, and Modified content plus a unified diff and statistics. Everything runs in your browser, and all text is HTML-escaped before display, so the diff is safe. The tool reports only what changed — it does not score quality, recommend, assess risk, or say which text is better.
Best for
- Seeing exactly what changed between two texts, word by word
- A mechanical, judgment-free git-style colored diff
- Spotting silent edits an AI made to your text
Not for
- Diffing two versions of a PROMPT with risk analysis — that is the Prompt Version Diff
- Judging which of two prompts is better — that is the Prompt Comparator
Use cases
- Seeing exactly what changed between two versions of a text
- Comparing two AI outputs from the same prompt
- Diffing two document or config versions line by line
- Catching a single swapped word in precise text
Pro tips
- Pick the mode for the content. Use Line mode for config, lists, and records where each line stands alone; Word mode for reworded prose; Mixed (the default) for most edits, where you want line structure plus word-level highlighting.
- Word-level marks are the fast path to subtle edits. A single inserted word or swapped term is easy to miss on a re-read but stands out inline in green or red here.
- The change count is mechanical, not a quality signal. Three changed lines is not better or worse than one — it is just what moved. The tool deliberately offers no verdict.
- Identical texts say so. If you get "no differences found", the two inputs match exactly, including whitespace — a quick way to confirm nothing changed.
FAQ
How is this different from the Prompt Version Diff?
Mechanics versus meaning. The Prompt Version Diff interprets two versions of a prompt: it analyzes facet changes (role, tone, format), risk deltas, and delivers a verdict — "Version B is a net improvement" or "a regression" or "mostly cosmetic". This tool shows the literal difference between any two texts — the words that were added, removed, and changed — and stops there. One tells you what a prompt revision means; the other shows you exactly what moved.
How is this different from the Prompt Comparator?
Showing versus deciding. The Prompt Comparator scores two independent prompts across quality dimensions and tells you which one is better and why. This tool neither scores nor recommends; it displays the difference between two texts and leaves every judgment to you. Same verb — "compare" — opposite intent: the Comparator decides a winner, the Diff Checker just shows the change.
Does it work on any text, or only prompts?
Any text. It is a general-purpose mechanical diff — documents, AI outputs, config files, contract clauses, lists, code snippets, drafts. There is no assumption that the input is a prompt, which is exactly what separates it from the prompt-specific tools. If you can paste it, it can diff it.
What do the three diff modes do?
Line mode compares whole lines and reports each as added, removed, or unchanged — best for config, lists, and structured text. Word mode highlights the exact words inserted and deleted inside changed regions — best for reworded prose where the line break does not matter. Mixed mode, the default, combines them: it keeps line structure but, for similar removed-and-added line pairs, highlights which words changed inside the line. Most edits read best in Mixed.
Does it score the changes or tell me which version is better?
No, by design. The Change Summary is a purely mechanical tally — lines and words added, removed, and changed. The tool offers no quality score, no recommendation, no risk assessment, and no "which is better". Its whole job is to show the difference accurately and let you decide what it means. If it judged the change, it would be a different tool.
Is my text safe — could a diff with HTML in it break the page?
It is safe. Because a diff has to render the texts you paste, every piece of your content is HTML-escaped before it is shown — a script tag or angle brackets in your input appear as literal characters in the diff, never as live markup. The colored view is built only from escaped content plus the tool's own markup, so pasting code, HTML, or markup is fine.
Is the diff deterministic?
Yes — the same two texts always produce the same diff, because it's a deterministic algorithm, not an AI comparison. Copy or download the diff report yourself.