Text Diff Tool
Compare two texts and see the differences line by line. Instantly spot additions, deletions, and unchanged lines with color-coded output. Free, private, and runs entirely in your browser.
Free Online Text Diff & Comparison Tool
Need to see what changed between two versions of a document, code file, or configuration? SmarterSources' Text Diff Tool compares two texts line by line and highlights every addition, deletion, and unchanged line with clear color coding. Everything runs 100% in your browser — your data is never sent to any server.
How It Works
Paste the original text on the left and the modified text on the right, then click "Compare." The tool uses a Longest Common Subsequence (LCS) algorithm to identify the minimal set of changes between the two texts. Deleted lines appear in red with a minus prefix, added lines appear in green with a plus prefix, and unchanged lines are shown normally for context.
Inline vs. Side-by-Side View
The inline (unified) view shows all changes in a single scrollable column, which is compact and familiar to anyone who uses git diff. The side-by-side view places the original and modified texts in two columns with aligned line numbers, making it easy to compare corresponding sections visually. Switch between views at any time without re-running the comparison.
Common Use Cases
This tool is useful for code reviews, document versioning, comparing configuration files, proofreading edits, verifying merge results, and any situation where you need to quickly see what changed between two pieces of text. Developers, writers, editors, and system administrators all benefit from a reliable text comparison tool.
Frequently Asked Questions
What is a text diff?
A text diff (short for "difference") is a comparison between two pieces of text that highlights what has changed. Lines that were removed are shown in red, lines that were added are shown in green, and unchanged lines are shown normally. This makes it easy to see exactly what changed between two versions of a document or code file.
What is the difference between inline and side-by-side diff?
Inline diff (also called unified diff) shows all changes in a single column, with deletions and additions interleaved. Side-by-side diff shows the original text on the left and the modified text on the right, with changes aligned horizontally. Inline is more compact, while side-by-side makes it easier to compare corresponding lines.
What algorithm does this tool use?
This tool uses the Longest Common Subsequence (LCS) algorithm to compute line-by-line differences. LCS finds the longest sequence of lines that appear in both texts in the same order, then marks everything else as added or removed. This is the same fundamental algorithm used by tools like git diff and GNU diff.
Is my data safe?
Yes. All text comparison happens entirely in your browser using JavaScript. Your data never leaves your device. SmarterSources does not collect, store, or transmit any text you enter into this tool.
Can I compare large files?
Yes. Since processing happens in your browser, the tool can handle reasonably large texts. Performance depends on your device's memory and processing power, but most modern devices can compare texts with thousands of lines without issues.
Does it support comparing code files?
Absolutely. The monospace font and line-by-line comparison make this tool ideal for comparing code files, configuration files, SQL queries, or any structured text. Simply paste the two versions and click Compare.