The Review Board diff viewer is one of the best on the market. It has

many ways to help you look through a change and focus on what's

important.
Here's just a few of the features we provide:



Detailed file index
The file index lists all the files modified in the diff, along with a

graph showing the relative number of inserts, deletes, and replaces.
The thickness of the ring shows how much of the file is modified (and

will be a full red or green circle, if the file is deleted or added).
The colored dots on the side link to the matching changed chunks for

that file.





Multi-line commenting
Click a line number, or click and drag down several lines to comment

on those lines.





Syntax highlighting
Every diff is syntax-highlighted, making it easier to see, for

instance, what's a string and what's a reserved keyword.
This supports highlighting file formats of all kinds.





Collapsable diffs
Diffs are shown collapsed, only showing what changed and the

immediate lines around it.
A header is shown above each change, showing the nearest function or

class. Clicking on the header will show all unchangedl ines up to

that function or class.
Alternatively, click the [+] 20 to show 20 more lines, or the [+]

to show all the lines hidden behind that header.





Moved code detection
Significant code changes that move around a file are specially shown

with little move flags saying where they went to or where they came

from. You can rely on these to know that you don't need to give that

code another look.
For example, see how the __init__ function was moved in /r/2/diff/





Indentation change indicators
When code is indented or un-indented, we show it cleanly without

showing a full line change. These are shown by >>>> and <<<<

markers on lines, which you can see in /r/2/diff/ and in

/r/2/diff/1-2/
Unlike most diff viewers, you won't have to waste your time examining

every line that was indented, looking for changes.
This will even differentiate between spaces and tabs. If someone

accidentally indents the wrong way, you'll know.





See changes made within a line
When replacing just part of a line, we highlight the changes, making

it much easier to see the addition of a word, renaming of a variable,

or even the accidental removal of a semicolon.





Interdiffs
When reviewing multiple iterations of a change, you can view an

"interdiff," the diff between two diffs. It's easy to see what has

actually changed. For example, see /r/2/diff/1-2/





Multi-commit diffs
Whether one commit or a hundred, you can post it to Review Board.
Reviewers can look at the entirety of your work as one change,

dig into individual commits, or view any range of commits they want.





Download any file in the diff
Simply click the little down arrow next to the "Revision" or "New

Change" in the diff's header to download the full content of either

the file on the left-hand side or right-hand side.



Click View Diff in the top-right to look at the diff for this review

request to play around with the diffs.