Utilumo
LightDarkSystem
Guide1 min readUpdated June 29, 2026

How to compare two texts (diff)

Short answer

A diff compares two pieces of text and highlights what was added, removed, or unchanged. It is the fastest way to see exactly how one version differs from another, whether for code, documents, or AI prompts.

What a diff shows

Instead of reading both versions and hunting for changes, a diff aligns them and marks the differences: additions, removals, and the parts that stayed the same. You see the change at a glance.

  • Added text, usually shown in one color
  • Removed text, shown in another
  • Unchanged text, shown plainly for context

Line vs word diffs

A line diff compares whole lines, which suits code and structured text. A word or character diff highlights smaller edits within a line, which is better for prose and prompts where only a few words changed.

Try it: Prompt DiffCompare two versions of a prompt or any text and see the differences locally.Open tool

When it helps

  • Iterating on an AI prompt and checking exactly what you changed
  • Reviewing edits to a document or message
  • Spotting an accidental change between two copies of text

References

Questions

What is the difference between a line diff and a word diff?

A line diff marks entire changed lines, which is good for code. A word diff highlights the specific words that changed within a line, which is clearer for prose and prompts.

Why compare two prompts?

When refining an AI prompt, small wording changes can shift the output. A diff shows precisely what you changed so you can connect a wording change to a result change.

Does the diff tool upload my text?

No. The comparison runs locally in your browser and your text is never uploaded.

Keep reading

Guide1 min readHow to write a better AI promptClear context, a specific task, and a defined output format make AI prompts far more reliable. Here is a practical structure and the habits that help.Read
Explainer1 min readWhat is prompt injection?Prompt injection is when hidden instructions in input trick an AI model into ignoring its real task. Here is how it works and how to reduce the risk.Read