Text Diff Checker
Compare two texts and show differences
Online Text and Code Comparison - Diff Checker
What is text and code comparison (diff) good for?
Text comparison, or diff, is fundamental for spotting the differences between versions of a document or of source code. The main use cases are code reviews, where you need to see exactly what a pull request changed; debugging, to identify which modification introduced a bug; checking that translations and localisations carry all of the original content; auditing configuration changes between environments; comparing program output for regression testing; and reviewing edits to technical documentation. This tool highlights added lines in green, removed lines in red and modified lines so changes jump out immediately.
How do text difference algorithms work?
Diff algorithms are built on finding the Longest Common Subsequence (LCS) between two texts: the longest sequence of elements appearing in both in the same order, though not necessarily consecutively. Lines inside the LCS count as unchanged; everything else is marked as added or removed. Advanced algorithms such as Myers (used by git), Patience Diff (better for code with many changes) and Histogram Diff (tuned for performance) improve the quality and readability of the output, which matters most in source code where structure carries meaning.
How do developers use code comparison every day?
Professional developers compare code constantly: reviewing pull requests on GitHub or GitLab before approving changes, running git diff to inspect local changes before committing, combining git blame with diff to find out when a bug appeared, resolving merge conflicts by comparing versions, auditing configuration differences between production and staging, verifying that a deployment carries the expected changes, and comparing test output between versions. Diff tools such as git diff, vimdiff, the VS Code diff view and this web tool are simply part of the job.
If you work with this tool, you will probably also find these useful Text Diff, Duplicate Remover, Gradient Generator, Flexbox Generator.
Frequently asked questions
Why does a line show as removed and added when only one character changed?
Traditional diff algorithms operate on whole lines. If any character on a line changes, the entire line counts as different: it appears removed from the original and added to the modified version. For a clearer view of small edits, some tools implement inline diff or word diff, which highlights the specific characters that changed inside the marked lines. On the command line, git diff --word-diff gives you that view.
How do I ignore whitespace changes when comparing?
This tool offers options to ignore whitespace differences: ignoring trailing whitespace at the end of lines, normalising runs of spaces to a single space, ignoring completely blank lines, or ignoring every whitespace difference. That is especially useful when comparing code formatted with different indentation styles (tabs versus spaces, 2 versus 4 spaces) or documents from different editors. Turn these options on when only real content changes matter to you.
Can I use this tool to compare binary files?
No, this tool is designed exclusively for plain text: source code, configuration files and text documents. For binary files such as images, PDFs, Word documents or executables you need specialised tooling: pixel-by-pixel image comparison, PDF diff tools that understand document structure, or byte-level comparison for generic binaries. For office documents, consider exporting to text or using the native track changes features.