1Review advisor revisions without track changes
LaTeX has no built-in track changes, so when a supervisor or co-author edits your chapter and sends the file back, the question is always the same: what did they actually change? Put your version in the left pane (original.tex) and theirs in the right pane (revised.tex), by pasting the source or dropping the .tex files. Removals show in red, additions in green, with a running count of added, removed and unchanged lines. If you loaded them the wrong way round, the Swap button flips the two sides.
2Line mode or word mode
Line mode compares whole lines, as git diff does: ideal for preamble changes, new equations or moved paragraphs. Word mode highlights the exact words that changed inside a line, which matters in LaTeX because a paragraph is often a single long line: a one-word correction would otherwise mark the whole paragraph. Both modes work in the unified view (one column, line numbers) and the side-by-side view (original and revised aligned row by row).
3Download a patch and apply it
The Download patch button saves changes.patch, a standard unified diff built line by line whatever mode is on screen (Copy diff instead copies a simple +/- listing, handy for an email). It is a Git-style patch for the file named next to the button (the last .tex you dropped in, main.tex by default; edit it if your file has another name or lives in a subfolder, e.g. chapters/intro.tex). From the folder that holds the file:
git apply --check changes.patch # check first git apply changes.patch # apply patch -p1 < changes.patch # same thing without Git
Keep the project under Git and every round of advisor revisions becomes one commit, with a proper history you can compare or roll back.
4Compare two arXiv versions
To see what changed between v1 and v2 of a preprint, download each version’s source from arXiv (the e-print link on the abstract page), extract both archives, and drop the matching main .tex files into the two panes. Word mode is usually the most readable here, since authors tend to rewrite sentences rather than lines.
Everything runs in your browser. Once the source looks right, open it in the live LaTeX preview to check the equations, or start a new chapter from one of the free templates.