Text Diff
Compare two blocks of text. Changed words are highlighted inline — removed in red, added in green, on the same line.
Paste the original text on the left and the modified version on the right, then click Compare.
About Text Diff
A text diff (short for "difference") is the result of comparing two pieces of text to find exactly what changed between them. Diff tools are essential in software development, technical writing, and any workflow where tracking changes matters. Instead of reading two documents side by side, a diff highlights additions, deletions, and modifications so you can focus on what's new.
How Diff Algorithms Work
Most diff tools — including this one — are built on the Longest Common Subsequence (LCS) algorithm. LCS finds the longest sequence of lines (or words) that appear in both texts in the same order. Everything not in the LCS is a difference: lines only in the original are "removed," and lines only in the modified version are "added." When a removed line and an added line appear next to each other, the tool merges them into a single "modified" line and applies word-level highlighting so you can see exactly which tokens changed.
Character, Word, and Line Diffs
Diffs can operate at different granularities. A line-level diff treats each line as an atomic unit — either the entire line matches or it doesn't. A word-level diff breaks lines into tokens and compares them individually, which is more useful when a single word changes in a long sentence. Character-level diffs go even further, highlighting individual letter changes. DevDash's Text Diff combines line-level comparison with word-level inline highlighting to give you the best balance between overview and detail.
Common Use Cases
Developers use diff tools daily during code review to see what a pull request changes. Operations engineers compare configuration files before and after deployments. QA teams diff API responses to verify that a new release returns the expected data. Writers and editors compare document drafts to track revisions. Migration engineers validate that transformed output matches expectations. In each case, a reliable diff tool saves time and prevents overlooked changes.
Diff in Version Control vs. Standalone Tools
Version control systems like Git have built-in diff capabilities tied to file history. Standalone diff tools like this one are useful when you need to compare arbitrary text that isn't tracked in a repository — for example, comparing a production config with a local draft, diffing two API responses from different environments, or checking whether a copy-paste introduced subtle differences. Because DevDash's diff runs entirely in your browser, your text never leaves your machine.
Frequently Asked Questions
What is a text diff?
A text diff is the result of comparing two pieces of text to identify exactly what changed between them. Additions, deletions, and modifications are highlighted so you can quickly see the differences without reading both versions side by side.
How do I compare two blocks of text online?
Paste the original text on one side and the modified version on the other, then click Compare. The tool runs a longest common subsequence algorithm to find matching and differing sections, displaying results with color-coded highlights for added, removed, and changed content.
What is the difference between character-level and line-level diff?
A line-level diff treats each line as a single unit and marks entire lines as added or removed. A character or word-level diff breaks lines into smaller tokens to show exactly which words or characters changed within a line. This tool combines both approaches for maximum clarity.
When should I use a standalone diff tool instead of Git diff?
Use a standalone diff tool when comparing arbitrary text that isn't tracked in a repository. Common examples include diffing API responses from different environments, comparing configuration files before deployment, or checking whether a copy-paste introduced subtle changes.
How is diff used in code review?
During code review, diff views show exactly which lines a pull request adds, removes, or modifies. Reviewers scan the highlighted changes to verify correctness, spot bugs, and ensure coding standards are followed without reading the entire file from scratch.