When code review happens outside a pull request
Most developers review code inside a Git workflow — a pull request on GitHub or GitLab, or git diff in the terminal. But a surprising amount of code review happens outside that flow.
A client emails you two versions of a script. A colleague pastes a config file in chat and asks "what changed?" You are debugging a production server where the file was edited directly and never committed. You are comparing a vendor's updated template against the one you customised. You copied a function from Stack Overflow and want to see exactly how it differs from yours. In all of these, the two versions exist as plain text, not as commits in a repository — so git diff has nothing to work with.
The basic workflow
Comparing two versions of a file visually takes three steps:
1. Put the original version in the left panel and the new version in the right panel of the Text & Code Difference Checker — paste directly, or upload the two files.
2. Set the language (JavaScript, Python, SQL, and 50+ others) so the code gets syntax highlighting, which makes it far easier to read than a plain terminal diff.
3. Read the side-by-side result: removed lines in red on the left, added lines in green on the right, with the changed portions within a line highlighted.
Because it renders in a browser with colour and syntax highlighting, this view is often easier to read than a unified diff in a terminal — especially when you are reviewing with someone who is not comfortable at the command line.
Choosing the right precision for code
How the tool highlights changes within a line matters a lot for code review:
Smart precision pairs each removed line with its most similar added line, then highlights the words that changed. This is the best default for most code review — you see that a line was edited and exactly which token changed.
Word precision diffs the changed block at the word level. Reach for this when a refactor changed the number of lines — three lines became two, or a statement was split across lines — because word mode is not confused by the line count changing.
Character precision highlights individual changed characters. This is ideal for the small, dangerous edits: a flipped comparison operator (< became <=), a renamed variable that differs by one letter, an off-by-one in an index, a changed string literal. These are exactly the bugs that slip through a quick read, and character mode makes them jump out.
What to look for when reviewing a diff
A visual diff shows you what changed; a good review asks whether the change is correct. A few things worth checking every time:
Logic changes hiding as small edits. A single character — a negated condition, a changed operator, an && that became || — can invert behaviour. Use character precision on suspicious lines.
Accidental deletions. Scan the red side for lines that were removed but probably should not have been — an error check, a null guard, a cleanup call. Removals are easy to miss because your eye is drawn to the new green code.
Whitespace-only churn. If a reformat touched every line, turn on "Ignore whitespace" so the real logic changes are not buried under indentation noise.
Scope of the change. "Hide unchanged" collapses the untouched lines so you see only what actually differs — a fast way to gauge how big a change really is before reading it in detail.
Sharing the review with someone else
One advantage of a browser-based diff over a terminal is that the result is easy to hand to another person. After comparing, use the Save or Share feature to generate a link to the exact diff you are looking at. The other person opens it in their browser — no repository access, no tools installed, no "can you paste it again."
This is genuinely useful for reviewing with a non-developer (a manager checking that a config value changed, a writer confirming which paragraph in a template moved) or for asking a teammate "does this change look right to you?" without setting up a branch and a pull request for what might be a five-line edit.
When to move the review into Git instead
This visual workflow is the right tool when the code is not in a repository, when you want a shareable and readable view, or for a quick one-off comparison. It is not a replacement for proper version control on real projects.
If the code lives in a repository and the change is something you will keep, review it as a pull request: you get line comments, review history, CI checks, and a permanent record of who approved what. The rule of thumb is simple — use a visual diff to answer "what changed here, right now" for loose files and quick checks; use Git and pull requests for changes that become part of a codebase you maintain over time. The two approaches complement each other rather than compete.