> For AI agents: the complete documentation index is available at /en/llms.txt, the full documentation bundle is available at /en/llms-full.txt.

# Text Diff

[Text Diff](https://tools.newzone.top/en/text-diff) is an offline two-pane text and file comparison tool. Beyond highlighting changes, it states in one sentence **which line and which field the first difference starts at** — so you don't have to hunt for the starting point in a screen full of red and green.

![Text Diff interface](/img/text-diff-en.webp "Text Diff interface")

:::tip 30-second quickstart

1. Paste text into each pane, or drag two files in
2. Glance at the detected format (plain / CSV / TSV / INI / JSON) and switch it if wrong
3. The banner spells out where the **first difference** is — click "Jump" to go there
4. Need to hand it to someone? "Export diff" gives you a `git apply`-ready `.patch`

:::

## First-difference locator

This is what sets the tool apart from a plain diff: the banner describes the first difference in natural language, phrased per format:

| Format             | Example message                        |
| ------------------ | -------------------------------------- |
| CSV / TSV          | Line 12, column 3 "price" differs      |
| INI                | Line 8, value of key "timeout" differs |
| Plain text         | Line 5, differs from character 17      |
| Added/removed line | Line 20: a line was added in B         |

Pair it with the Previous / Next buttons to step through blocks; the header also shows "block i of n".

## Format detection

Detection combines file extension and content, and can always be overridden:

- **Plain text**: line-by-line comparison
- **CSV / TSV**: guesses the delimiter first (whichever of `,` `\t` `;` `|` yields the most consistent column count), then compares by column, handling quoted fields and `""` escapes
- **INI**: compares key/value pairs and names the key whose value changed
- **JSON**: currently compared as text lines (a notice is shown)

## Comparison options

- **Ignore surrounding whitespace**: skip differences caused by edge spacing
- **Ignore case**: skip letter-case differences
- **Character-level diff**: within a modified row, mark exactly which characters changed (off by default)
- **Only differences**: fold away identical content, keeping just the diff blocks
- **Context lines**: how many lines to keep around each difference when folding — "Only differences" or ±N lines

## Views and navigation

- **Split / Unified**: switch between the side-by-side and inline views at any time
- **Maximize**: full-screen mode for long files
- **Swap A/B**: exchange the two sides in one click
- **Expand folds**: identical runs collapse to "⋯ N identical lines hidden (click to expand)"
- **Stats**: similarity percentage, line counts for A and B, and "N differences · X modified / Y added / Z deleted"

## Performance guard

When the two sides diverge heavily, a line-level diff can take a long time. A **3-second timeout** stops the run and shows "comparison timed out" rather than hanging the page. Click "Compare anyway" to force a full run with no time limit for that comparison. Any content change re-arms the guard.

## Encoding detection

Uploaded files are auto-detected as UTF-8, GBK, Big5, UTF-16LE, and other common encodings, with the detected value displayed; a manual switch re-decodes the file. Especially useful for CSVs exported from different systems, GBK config files in legacy projects, and Windows logs.

## Export

- **Copy A / Copy B**: copy either side out
- **Export diff**: generate a standard unified diff (`.patch`) for `git apply` or a code review tool. The filename defaults to B's filename

## Common patterns

- **Verify a config change**: drop in two `.ini` / `.env` files and read off which key's value moved
- **Compare tabular data**: two exported CSVs, located down to the exact field
- **Self-review before a PR**: compare local changes against the deployed version and export a `.patch`
- **Proofread a translation**: enable "Ignore surrounding whitespace" to see only substantive edits between revisions

Everything runs locally in your browser — **nothing is uploaded** — safe for sensitive configs and private code.