Duplicate lines
A B A → A A B
The shortest-edit calculation keeps repeated lines aligned without treating every later occurrence as changed.
🔍Text Diff CheckerReady
Text and files stay in this browser. Local text files are limited to 5.00 MB. Exact alignment is dynamically bounded to protect the tab; character-level exact comparison is limited to 200,000 source characters per side. When an exact result is unsafe, the tool shows a whole-document replacement summary instead. Patch export always uses a strict line diff, even when the display ignores case or whitespace.
0 lines · 0 B
0 lines · 0 B
Capability checkedVerified September 9, 2026
What works
- Compute a Myers shortest-edit-script diff
- Switch between line, word/token, and character granularity
- Optionally ignore letter case or normalize whitespace changes
Important limits
- Large or highly divergent texts can be slow and memory-intensive
- Character mode compares Unicode code points rather than grapheme clusters, so some emoji and combining sequences can be split
What the Text Diff Checker does—and does not do
Exact supported inputs, outputs, limits, and primary sources for the current implementation.
Accepted input
- Two plain-text values pasted or opened from local text files up to 5 MB
- Unicode text compared by line, word/token, or Unicode code point
Produced output
- Inline or side-by-side highlighted differences
- Old and new line numbers for line comparisons
- Counts of added, removed, modified, and unchanged units
- A labelled whole-document replacement summary when an exact diff would exceed the browser safety cap
- A downloadable unified .diff patch when a strict line comparison completes safely
Operational limits
- Opened local files are limited to 5 MB; pasted text is processed in browser memory
- Exact Myers alignment is dynamically bounded; extremely divergent inputs fall back to a whole-document replacement summary
- Character-level exact comparison is limited to 200,000 source characters per side; line and word modes remain available for larger text
Known limitations
- Large or highly divergent texts can be slow and memory-intensive
- Character mode compares Unicode code points rather than grapheme clusters, so some emoji and combining sequences can be split
- The comparison and .diff export are not syntax-aware; patch export intentionally ignores display-only case and whitespace rules and is unavailable in the whole-document replacement fallback
- Binary files and document formats are not supported
Standards and primary sources
Continue the workflow
Capability claims last reviewed September 9, 2026. Review dates describe the implementation audit, not content freshness by itself.
Use the Text Diff Checker with the right expectations
The comparison preserves duplicate lines and original newline endings instead of relying on a look-ahead heuristic. Open local text files or paste two versions, then choose the granularity that matches the review. The browser bounds worst-case exact-diff work: if two inputs are too divergent, it reports a whole-document replacement rather than inventing partial alignment. Display-only ignore rules never alter the original text, and patch export is available only when the strict line diff can reproduce the change.
When it is the right tool
- Reviewing configuration and code snippets
- Finding wording changes
- Comparing duplicate-heavy lists
- Checking newline-sensitive text before a patch handoff
A deliberate choice
Tooleras keeps this page specific to the job above instead of claiming support for adjacent formats, platforms, or edge cases it cannot verify. Open the capability guide for the exact inputs, outputs, limits, and sources.
Checked examples
Display rules versus patch output
HELLO → hello with “Ignore case” enabled
The display can treat the text as equal, but exported .diff output still contains the real case change so applying it reproduces the modified file.
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