How does the diff algorithm work?

This tool uses a line-by-line diff algorithm (similar to GNU diff) that finds the longest common subsequence between the two texts, then marks lines as added, removed, or unchanged.

How are whitespace changes handled?

Yes. By default, leading and trailing whitespace changes make lines different. Enable 'Ignore leading and trailing whitespace' to compare trimmed line content instead.

What do the diff prefixes mean?

Unified view prefixes added lines with '+', removed lines with '−', and unchanged lines with a space. Side-by-side view separates the original and modified text.

Can I diff code files?

Yes — paste any plain text including source code, JSON, HTML, or prose. The diff is purely text-based with no language-specific processing.

No. Comparison runs in your browser, and pasted text is not uploaded to a server.

What do the added and removed counts show?

The counts show added and removed lines in the computed line diff. Unchanged lines are excluded from both counts.

Does it compare individual characters?

The checker compares complete lines, so it is best for source files, configuration, documents, and other text where line-level changes matter.

Are empty lines preserved?

Yes. Empty lines are retained as line entries, allowing blank-line additions, removals, and changes to remain visible in the result.

Text Tools

Text Diff Checker

Compare two texts line by line and highlight additions and removals. Switch between unified and side-by-side views — copy the diff output instantly.

Line-by-Line Diff
Unified & Side-by-Side
Add / Remove Count
Ignore Case
Browser-only

Compare Text

Text 1 (original)

Text 2 (modified)

Display Options

Whitespace

Ignore leading and trailing whitespace

Paste two texts and click Compare

Text Diff Checker

Compare two versions of text in your browser. Text Diff Checker finds the longest common subsequence of lines, then reports added, removed, and unchanged lines. Use unified output for a compact review or side-by-side output when comparing the original and modified versions separately.

How line comparison works

The checker splits each input at line breaks and preserves line order. Matching lines are treated as unchanged. When a line exists only in the first input, it is marked removed; when it exists only in the second input, it is marked added. This produces a minimal line-oriented diff without requiring a programming language parser.

Unified output uses familiar prefixes:

Prefix	Meaning
`+`	Line added to modified text
`−`	Line removed from original text
Space	Line unchanged

Added and removed line totals appear above the result. Blank lines remain part of the comparison, which makes the tool useful for formatting and document review as well as source code.

Ignore surrounding whitespace

Enable the whitespace option when indentation or trailing spaces should not create a difference. The option trims each line before comparison. It does not perform character-level comparison, collapse internal spaces, or change the text shown in either input. Leave it disabled when whitespace carries meaning, such as Python indentation, Markdown formatting, or fixed-width data.

Common uses

Review code, configuration, JSON, CSV, SQL, and markup changes
Compare document revisions before publishing
Check generated output from scripts or build tools
Verify copy edits and line breaks
Find accidental blank lines or trailing-space changes

Browser-only comparison

Pasted text stays in the page while comparison runs locally. No account, upload, or language-specific parser is required. For sensitive source code or documents, this local workflow avoids sending content to a remote comparison service.

Example inputs

const port = 3000;
startServer(port);

const port = 8080;
startServer(port);

The unified result identifies the first line as removed and the replacement as added. The side-by-side view shows each version as its own copyable output.

Using a diff in development workflows

For command-line workflows, Git remains useful for repository history and patches:

git diff -- file.ts

For a quick browser comparison, paste the old and new content into this tool. It is language-agnostic, so the same process works for prose, source code, structured text, and generated files.

Frequently asked questions

Does the checker compare characters? No. It compares complete lines. Use a character-level editor when individual word or character changes need inline highlighting.

Does it modify my input? No. Inputs remain editable, and the result is computed only when Compare is clicked. Enable whitespace ignoring before comparing when outer spaces should be excluded.

Frequently Asked Questions

How does the diff algorithm work?: This tool uses a line-by-line diff algorithm (similar to GNU diff) that finds the longest common subsequence between the two texts, then marks lines as added, removed, or unchanged.
How are whitespace changes handled?: Yes. By default, leading and trailing whitespace changes make lines different. Enable 'Ignore leading and trailing whitespace' to compare trimmed line content instead.
What do the diff prefixes mean?: Unified view prefixes added lines with '+', removed lines with '−', and unchanged lines with a space. Side-by-side view separates the original and modified text.
Can I diff code files?: Yes — paste any plain text including source code, JSON, HTML, or prose. The diff is purely text-based with no language-specific processing.
Is my text private?: No. Comparison runs in your browser, and pasted text is not uploaded to a server.
What do the added and removed counts show?: The counts show added and removed lines in the computed line diff. Unchanged lines are excluded from both counts.
Does it compare individual characters?: The checker compares complete lines, so it is best for source files, configuration, documents, and other text where line-level changes matter.
Are empty lines preserved?: Yes. Empty lines are retained as line entries, allowing blank-line additions, removals, and changes to remain visible in the result.

Disclaimer

This tool is provided for general informational and utility purposes only. Results may be inaccurate, incomplete, outdated, or contain errors. Always verify results before relying on or using them.

Some tools may use AI, automated processing, third-party services, or server-side processing. Do not rely on these tools as a substitute for professional advice.

Use at your own risk. BestToolOnline makes no guarantees regarding the accuracy, reliability, completeness, availability, or suitability of results, to the maximum extent permitted by applicable law.

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Text Diff Checker

How line comparison works

Unified output uses familiar prefixes:

Prefix	Meaning
`+`	Line added to modified text
`−`	Line removed from original text
Space	Line unchanged

Added and removed line totals appear above the result. Blank lines remain part of the comparison, which makes the tool useful for formatting and document review as well as source code.

Ignore surrounding whitespace

Common uses

Review code, configuration, JSON, CSV, SQL, and markup changes
Compare document revisions before publishing
Check generated output from scripts or build tools
Verify copy edits and line breaks
Find accidental blank lines or trailing-space changes

Browser-only comparison

Example inputs

const port = 3000;
startServer(port);

const port = 8080;
startServer(port);

The unified result identifies the first line as removed and the replacement as added. The side-by-side view shows each version as its own copyable output.

Using a diff in development workflows

For command-line workflows, Git remains useful for repository history and patches:

git diff -- file.ts

For a quick browser comparison, paste the old and new content into this tool. It is language-agnostic, so the same process works for prose, source code, structured text, and generated files.

Frequently asked questions

Does the checker compare characters? No. It compares complete lines. Use a character-level editor when individual word or character changes need inline highlighting.

Does it modify my input? No. Inputs remain editable, and the result is computed only when Compare is clicked. Enable whitespace ignoring before comparing when outer spaces should be excluded.