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Text Compare text comparison tool

Quickly compare the differences between two pieces of text, supporting three comparison modes: character, single word, line, and Unified Diff view. Suitable for comparison and analysis of program code, configuration files, AI output and general text.

compare mode

View mode

Options Ignore case ignore whitespace ignore empty lines

Text A

0 characters

Text B

0 characters

Text Compare Complete Guide to Text Comparison

Gain an in-depth understanding of text comparison principles, Diff algorithms and usage scenarios

What is Text Compare?

Text Compare is a tool used to compare the differences between two pieces of text. It can quickly find the similarities and differences between the texts. Whether it's code version control, file modification tracking, AI output comparison, or simple content proofreading, text comparison tools can help you identify changes at a glance.

Compared with manual line-by-line comparison, the Text Compare tool can automatically identify added, deleted, and modified content and highlight them in different colors, greatly improving efficiency and accuracy. This tool supports Character、Word and Line Three comparison granularities meet the needs of different scenarios.

What is Diff?

Diff(abbreviation for Difference) refers to the process and results of calculating the difference between two text files or content. The output of Diff usually shows which lines have been added, deleted or modified, and is a core technology in version control systems (such as Git) and code review processes.

A standard Diff output contains the following elements:

Added: Marked in green, it indicates content that appears in the second paragraph of text but not in the first paragraph.
Deleted: In red, content that was present in the first paragraph of text but was removed in the second paragraph.
Modified: Marked in yellow, it means that the content has changed but has not been completely added or deleted.
Equal: The unchanged part, used as the baseline context for comparison.

Git Diff principle

Git's Diff function is based on Myers difference algorithm(Proposed by Eugene W. Myers in 1986), this is an algorithm that can find the longest common subsequence (LCS) between two sequences in O(ND) time complexity.

The core idea of Myers algorithm is in a Edit Graph Find the shortest path in:

Consider the two paragraphs of text as the X-axis and Y-axis of the two-dimensional grid.
When the characters in the two positions are the same, they can be moved diagonally (no editing times are consumed).
The goal of the algorithm is to find a path from the origin (0,0) to (N,M) that has the most diagonal movement (i.e., the most common parts).
The "off-diagonal movement" corresponding to this path is the required editing operation (add or delete).

The output format of Git Diff is also this tool Unified Diff The basis of the pattern. Unified Diff with --- and +++ Mark the file name with @@ ... @@ Mark the changed location with +(new) and - The (delete) prefix indicates the type of change for each row.

When is it appropriate to use the text comparison tool?

The text comparison tool is particularly useful in the following scenarios:

Code version comparison: Compare different versions of source code to quickly locate modification points. Very helpful for Code Review and Debug.
Profile comparison: Compare the differences between the two configuration files (such as JSON, YAML, ini) before and after to avoid mistaken changes or omission of key configurations.
AI output quality verification: Compare the output results of AI models under different prompts, or compare the response differences of the same prompt in different models to find the optimal results.
Document revision tracking: Track the modification history of contracts, reports, articles and other documents, and clearly display the specific content of each edit.
Content plagiarism detection: Quickly compare the similarity between two paragraphs of text to help determine whether there is plagiarism or unauthorized quotation in the content.
Data migration verification: After database migration or format conversion, compare the data content before and after conversion to ensure the correctness and completeness of the conversion.
Localization and translation proofreading: Compare the original text and the translated text to check whether there are missing, repeated or inconsistent paragraphs.

How is similarity calculated?

Similarity Score is a quantitative indicator of how similar two pieces of text are, ranging from 0% (completely different) to 100% (exactly the same). This tool calculates using the following formula:

Similarity = (number of common characters × 2) ÷ (length of Text A + length of Text B) × 100%

Where "number of common characters" is based on Longest common subsequence (LCS) Calculated by algorithm. LCS refers to the longest subsequence that appears in both sequences and maintains the original order. The longer the LCS, the more common parts the two paragraphs have in common, and the higher the similarity.

In line comparison mode, the similarity is calculated in "line" units; in character comparison mode, it is calculated in "character" units, providing a more refined similarity evaluation.

Text Compare FAQ

Q1: What are the differences between the three comparison modes: character, single word, and line?

Character Compare: Compare on a per-character basis, suitable for pinpointing spelling differences or minor text changes.
Word Compare: Comparison is done in units of words, suitable for comparing differences at the sentence or paragraph level, such as before and after the article is modified.
Line Compare: Compare each line of text as a unit, the behavior mode closest to Git Diff, suitable for version comparison of program code and structured text.
It is recommended to choose the most appropriate granularity based on your usage scenario: if you need to be precise down to letters, choose "Character", if you want to compare article paragraphs, choose "Single Word", and for code version control, choose "Line".

Q2: What is the difference between Side-by-Side and Unified Diff viewing modes?

Side-by-Side (left-right comparison): Display two pieces of text side by side, with Text A on the left and Text B on the right, with the difference lines highlighted in color. This mode is intuitive and easy to understand, and conforms to traditional text comparison usage habits.
Unified Diff: Combine two paragraphs of text into a unified view to - The prefix indicates deleted lines,+ The prefix marks the new line and ends with @@ The block header indicates the location of the change. This is the format closest to the output of the Git Diff command and is loved by developers.
It is recommended to use Side-by-Side mode for desktop environments. Unified Diff mode on mobile devices provides a better reading experience on narrow screens. This tool will automatically switch to a suitable display mode on the mobile phone.

Q3: What are the functions of "Ignore case", "Ignore blanks" and "Ignore blank lines" in the options?

Ignore Case: When comparing, the case of English letters is not distinguished, and "Hello" and "hello" will be regarded as the same. Suitable for comparing case-insensitive content.
Ignore Whitespace: Ignore differences in all whitespace characters (spaces, tabs, etc.) when comparing. Suitable for comparing program codes because differences in indentation styles do not affect logic.
Ignore Empty Lines: Do not treat empty lines as valid differences when comparing. If two paragraphs of text differ only in the number of blank lines, they will be treated as identical when this option is enabled.
These options can be used in combination to help you filter out uninteresting differences and focus on substantive changes.

Q4: What does the similarity score (Similarity) of text comparison represent?

A similarity score is a 0% to 100% metric that quantifies how similar two pieces of text are. 100% means the two paragraphs are identical, 0% means they have nothing in common. The calculation is based on the Longest Common Subsequence (LCS):
Similarity = (2 × LCS length) ÷ (Text A length + Text B length) × 100%
Generally speaking, a similarity above 90% means there are only minor differences; a similarity between 70% and 90% means there are some modifications; a similarity below 70% means there are major changes. Please note that the similarity is for reference only, and actual differences still require Diff viewing to confirm the specific changes.

Q5: Will text content be uploaded to the server? Is privacy safe?

Not at all. This tool isPure front-end application, all text comparisons, difference calculations and similarity analysis are done locally in your browser, no data is sent to the server. You can confidently compare any confidential content, including source code, business documents or personal data. This tool works even when offline.

Q6: How to export the difference report? What formats are supported?

You can use "Copy results button to copy the Diff results to the clipboard, or viaDownload report” button to download the difference report as a plain text file (.txt). The downloaded report contains the full Unified Diff format output, including archive headers, block position markers, and diff line content, suitable for saving or sharing with your team. Side-by-Side mode diff results are automatically converted to human-readable markup format when copied.