"Just compare these two files" turns out to mean different things depending on size. A short document edit and a huge exported log file need different handling to stay both accurate and fast.
For everyday edits: word-level detail matters
Knowing that a line changed doesn't tell you whether it was one word or the whole sentence. Word-level highlighting inside a changed line — showing exactly which words were added or removed — is what actually saves the re-reading. This is the common case for comparing drafts, contracts, config snippets, or two versions of structured data like JSON, XML, CSV, HTML, Markdown, or YAML.
For huge files: the naive approach chokes
Rendering every single line of a 50,000-line log file into the page at once is exactly what makes a browser tab freeze. The fix isn't a smarter diff algorithm so much as smarter rendering: collapse long unchanged runs into a single toggle instead of drawing every identical line, and trim large common prefixes/suffixes before comparing at all. The result stays fast even on files far too big to diff line-by-line by eye.
Getting a shareable record of what changed
A visual diff is great for reviewing a change yourself, but sharing "here's what changed" with someone else usually needs an actual file — a downloadable report listing every difference is worth more than a screenshot of a highlighted comparison.
Picking the right tool for the job
For typical documents, code, or structured data, Compare Documents gives full word-level highlighting across text, JSON, XML, CSV, HTML, Markdown, and YAML. For anything too large to comfortably render line-by-line — huge logs, big CSV exports, long data dumps — Text Compare is built specifically to stay fast at that scale, with collapsible unchanged sections and a downloadable diff report. Both run entirely in your browser, so nothing you're comparing is ever uploaded.
