Text Diff Checker — Compare Two Texts Side by Side

How to Compare Two Texts

Comparing two pieces of text with Pixab AI's diff checker is straightforward. Paste your original text into the left panel labelled Original and your revised or modified version into the right panel labelled Modified. The text can be anything — a paragraph, a legal clause, a configuration file, a poem, or source code.

Before comparing, choose your comparison mode using the segmented control: Line for line-by-line differences, Word for word-level changes within lines, or Character for character-by-character changes. For most use cases, Line mode is the right starting point. Click Compare to run the comparison.

The diff view appears below with a side-by-side layout. Removed text is highlighted in red on the left; added text is highlighted in green on the right. Unchanged text appears in grey, providing context around the changes. A statistics bar shows the total count of added, removed, and unchanged units so you can immediately quantify how much has changed. To share or archive the result, click Copy diff as text to get the differences in standard unified diff format — compatible with version control systems and diff tools everywhere.

When to Use a Diff Tool

Diff tools are most often associated with software development, but their usefulness extends to any situation where you need to understand precisely what changed between two versions of a text. Here are the most common real-world use cases:

Proofreading Edited Documents

When a colleague or editor returns a revised draft, it can be time-consuming to read the entire document again looking for changes — especially in long reports or proposals. A diff tool lets you compare the original and edited versions instantly, highlighting every insertion and deletion. You can focus your review on just the changed sections rather than rereading unchanged paragraphs. For further text analysis of the result, try our Word Counter to check the final length.

Legal Contract Review

In contract negotiations, changes between drafts are often subtle but critically important. A missing word, a changed date, or a swapped clause can have significant legal consequences. Comparing contract versions in a diff tool surfaces every change, no matter how small. Legal professionals and business teams use diff tools to verify that only agreed-upon amendments appear in the final version before signing.

Comparing Code Configurations

Configuration files — for web servers, CI pipelines, infrastructure-as-code, or application settings — often evolve over time or differ between environments (development vs. production). Pasting two versions of a configuration into our diff checker immediately shows which keys have changed, been added, or been removed. This is faster than manually scanning two large YAML, JSON, or TOML files side by side. For reformatting configuration after comparison, use our Text Cleaner to normalise whitespace.

Plagiarism Checking

When you suspect that one text was derived from another, a diff tool gives you immediate visual evidence. Sections that match will appear as unchanged (grey); sections that differ will be highlighted. This is useful for educators checking student submissions against a reference, journalists verifying if a press release has been altered, or content managers checking that republished articles match the original. A high proportion of unchanged lines in character or word mode indicates close similarity.

Verifying Translated Documents

When a document is updated in one language and the translation needs to be updated too, comparing the original-language versions (old and new) tells translators exactly which paragraphs changed and need re-translation. This prevents having to re-read the entire document in a foreign language looking for differences.

Tracking Changes Without Track Changes

Not everyone uses word processors with built-in change tracking. Plain text files, emails, and web-based editors often lack this feature. A standalone diff tool fills this gap — paste the before and after versions of any text, regardless of where it was edited, and instantly see a colour-coded summary of every change. For repetitive find-and-replace operations on your text, combine this tool with our Find and Replace tool.

Line vs Word vs Character Diff Explained

Choosing the right comparison granularity dramatically affects how useful the diff output is. Each mode is optimised for different types of content and different kinds of changes.

Line Diff — Best for Structured Text and Code

Line diff compares texts line by line. A line is considered changed only if the entire line is different. This is the mode used by most version control systems (Git, SVN) and is ideal for source code, configuration files, CSV data, and any text where lines are the logical unit of content. If you change one word in a line, the entire line appears as removed (red) and re-added (green). This can look noisier for prose but is exactly what developers need to see which lines of code are affected.

Word Diff — Best for Prose and Documentation

Word diff breaks each line into individual words and compares them. This means that if you change one word in a sentence, only that word is highlighted — the rest of the line shows as unchanged. Word diff is the most readable mode for documents, articles, blog posts, and any text where you want to see exactly which words were added, removed, or changed without the noise of entire lines being flagged. It is similar to how Microsoft Word's Track Changes feature displays edits.

Character Diff — Best for Short Texts and Precise Changes

Character diff is the most granular mode. Every single character is compared individually. This is most useful for very short texts — a single sentence, a URL, a string of code — or when you need to find subtle changes like a changed digit, a swapped letter, or a different punctuation mark. For long documents, character diff produces very dense output that can be hard to read, so use it sparingly and only when you genuinely need character-level precision.

Diff in Software Development — A Primer for Non-Developers

The word “diff” comes from a Unix command-line utility (also called diff) created in the 1970s that compared two text files and output the differences. Software developers use diff tools constantly — every time a developer submits code for review, the review interface shows a diff of what changed.

Git, the most widely used version control system, stores the history of a project as a series of diffs rather than full copies of every file. This makes repositories compact and makes it possible to see exactly what changed in each commit. When you run git diff, Git shows you the differences between your working copy and the last saved version of your code — the same concept as our online diff tool, applied to entire codebases. The unified diff format that our “Copy diff as text” button generates is the same format used by Git, making it compatible with any tool in the developer ecosystem.

Document Comparison Tools Compared

Several tools exist for comparing documents, each with different strengths. Our online diff checker focuses on plain text comparison with maximum privacy and zero friction.

Microsoft Word Track Changes is excellent for collaborative editing within Word documents, but it only works with .docx files, requires Word to be installed, and tracks changes as they happen rather than comparing two finished versions. If you have a final v1 and final v2 Word document without tracked changes, Word's “Compare Documents” feature can help, but it requires opening both files in Word.

Google Docs Suggestions works similarly to Word Track Changes — it shows inline changes as suggestions, but it is designed for real-time collaborative editing rather than comparing two finished texts. It also only works with Google Docs files.

Our tool works with any plain text — regardless of its origin. Paste content from any source (Word, Google Docs, a terminal, a website, a database export) and compare instantly without uploading files or creating accounts. For additional text operations after comparison, use our Find and Replace tool to make targeted corrections.

Frequently Asked Questions

Is my text uploaded to a server?

No. All comparison operations run in your browser using JavaScript. Your text never leaves your device. This makes the tool safe for confidential documents, proprietary code, legal contracts, and personal data.

What is the maximum text size I can compare?

There is no enforced limit. The comparison runs in your browser's available memory, which is typically several hundred megabytes on modern devices. Very large texts (tens of thousands of lines) may take a moment to process, but there is no server-side cap.

What does “Copy diff as text” output?

It outputs the differences in unified diff format — the same format used by Git and other version control systems. Lines prefixed with + are additions; lines prefixed with - are removals; unchanged lines appear without a prefix for context.

Which mode should I use for comparing code?

Line mode is almost always the right choice for code. It matches how Git and most code review tools display diffs, making the output familiar and easy to interpret for developers. Use word mode if you want to see exactly which tokens within a line changed.

Can I compare non-English text?

Yes. The diff algorithm operates on Unicode strings, so any language — Arabic, Chinese, Urdu, Cyrillic — works correctly in line and word mode. Character mode also handles multi-byte Unicode characters correctly.

What does the stats bar show?

The stats bar shows the count of added units, removed units, and unchanged units in the selected mode. In line mode, these are line counts. In word mode, they are word counts. In character mode, they are character counts.

Does the tool handle very similar texts well?

Yes. The underlying diff algorithm (based on the Myers diff algorithm, the same one used by Git) is optimised for finding the minimal set of differences between two texts. Even when texts are nearly identical, it accurately identifies just the changed portions rather than showing everything as different.