Text Compare

How it works

• Paste the original text into the first box.
• Paste the version you want to compare into the second box.
• The tool shows unchanged lines, removed lines (-), and added lines (+).

Use cases

How diff algorithms find what changed

This tool uses the same core idea as programming diff tools: the longest common subsequence (LCS). It finds the largest set of lines the two texts share in order, then marks everything outside that set as removed (-) or added (+). This is why a single edited line shows as one removal plus one addition — the algorithm sees an old line that vanished and a new line that appeared.

Line-based comparison is the sweet spot for most real work: it is precise enough to pinpoint changes and coarse enough to stay readable. For prose, putting each sentence on its own line before comparing gives you sentence-level precision.

Practical comparison workflows

Common uses: verifying which requirements changed between two versions of a client brief, checking what a colleague edited in a shared document when track-changes was off, comparing two exported configuration files, and confirming that a pasted backup matches the original. For list reconciliation — which emails are in list A but not list B — sort both lists first (our Alphabetical Order tool) so the diff aligns matching lines instead of flagging ordering differences.

Diff, list, CSV, or JSON: pick the right comparison

A line diff answers "what changed between these two versions" and is the right tool for prose, code and configuration where order is meaningful. It is the wrong tool for a list, because a diff of two lists that contain the same items in a different order reports that everything changed.

List comparison treats each side as a set and answers the question people usually mean: what is in the first list only, the second only, and both. That covers the common jobs — reconciling two email exports, finding which SKUs are missing from a feed, checking which of last month’s entries survived. Duplicates within a side are collapsed, and the comparison is case-insensitive unless you turn that off, because "Apple" and "apple" are nearly always the same record.

CSV comparison parses both sides as tables, so it can report changed cells by row and column rather than as whole changed lines, which is far easier to act on. JSON comparison parses both documents and compares by path, so reformatting and key reordering are correctly treated as no change at all — something a text diff cannot do and which otherwise buries one real difference under a hundred cosmetic ones.

FAQ