---
stage: Create
group: Code Review
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://handbook.gitlab.com/handbook/product/ux/technical-writing/#assignments
---
# Changes in merge requests **(FREE ALL)**
A [merge request](index.md) proposes a set of changes to files in a branch in your repository. These
changes are shown as a _diff_ (difference) between the current state and the proposed
changes.
By default, the diff view compares the versions of files in the merge request source branch
to the files in the target branch, and shows only the parts of a file that have changed.
For technical details on how GitLab calculates the diff between the two revisions,
read [Working with diffs](../../../development/merge_request_concepts/diffs/index.md)
in our development documentation.
## Show all changes in a merge request
To view the diff of changes included in a merge request:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Merge requests** and find your merge request.
1. Below the merge request title, select **Changes**.
1. If the merge request changes many files, you can jump directly to a specific file:
1. Select **Show file browser** (**{file-tree}**) or press F to display the file tree.
1. Select the file you want to view.
1. To hide the file browser, select **Show file browser** or press F again.
Files with many changes are collapsed to improve performance. GitLab displays the message:
**Some changes are not shown**. To view the changes for that file, select **Expand file**.
## Show one file at a time
For larger merge requests, you can review one file at a time. You can change this setting
[temporarily in a merge request](#in-a-merge-request-show-only-one-file-at-a-time), or
so it [applies to all merge requests](#in-all-merge-requests-show-only-one-file-at-a-time).
### In a merge request, show only one file at a time
To temporarily change your viewing preferences for a specific merge request:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Merge requests** and find your merge request.
1. Below the merge request title, select **Changes**.
1. Select **Preferences** (**{settings}**).
1. Select or clear the **Show one file at a time** checkbox.
This change overrides your choice in your user preferences. It persists until you
clear your browser's cookies or change this behavior again.
### In all merge requests, show only one file at a time
To view one file at a time for all of your merge requests:
1. On the left sidebar, select your avatar.
1. Select **Preferences**.
1. Scroll to the **Behavior** section and select the **Show one file at a time on merge request's Changes tab** checkbox.
1. Select **Save changes**.
After you enable this setting, GitLab displays only one file at a time when you review
merge requests. To view other changed files, either:
- Scroll to the end of the file and select either **Prev** or **Next**.
- Select **Show file browser** (**{file-tree}**) and select another file to view.
## Compare changes inline
You can view the changes inline:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Merge requests** and find your merge request.
1. Below the title, select **Changes**.
1. Select **Preferences** (**{settings}**).
1. In the **Compare changes** area, select **Inline**.
The changes are displayed after the original text.
## Compare changes side-by-side
Depending on the length of the changes in your merge request, you may find it
easier to view the changes inline, or side-by-side:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Merge requests** and find your merge request.
1. Below the title, select **Changes**.
1. Select **Preferences** (**{settings}**).
1. In the **Compare changes** area, select **Side-by-side**.
The changes are displayed across from one another.
## Expand or collapse comments
When reviewing code changes, you can hide inline comments:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Merge requests** and find your merge request.
1. Below the title, select **Changes**.
1. Scroll to the file that contains the comments you want to hide.
1. Scroll to the line the comment is attached to, and select **Collapse** (**{collapse}**):
To expand inline comments and show them again:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Merge requests** and find your merge request.
1. Below the title, select **Changes**.
1. Scroll to the file that contains the collapsed comments you want to show.
1. Scroll to the line the comment is attached to, and select the user avatar:
## Ignore whitespace changes
Whitespace changes can make it more difficult to see the substantive changes in
a merge request. You can choose to hide or show whitespace changes:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Merge requests** and find your merge request.
1. Below the title, select **Changes**.
1. Before the list of changed files, select **Preferences** (**{settings}**).
1. Select or clear the **Show whitespace changes** checkbox:
## Mark files as viewed
> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/51513) in GitLab 13.9 [with a flag](../../../administration/feature_flags.md) named `local_file_reviews`. Enabled by default.
> - [Feature flag removed](https://gitlab.com/gitlab-org/gitlab/-/issues/296674) in GitLab 14.3.
When reviewing a merge request with many files multiple times, you can ignore files
you've already reviewed. To hide files that haven't changed since your last review:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Merge requests** and find your merge request.
1. Below the title, select **Changes**.
1. In the file's header, select the **Viewed** checkbox.
Files marked as viewed are not shown to you again unless either:
- New changes are made to its content.
- You clear the **Viewed** checkbox.
## Show merge request conflicts in diff
> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/232484) in GitLab 13.5 [with a flag](../../../administration/feature_flags.md) named `display_merge_conflicts_in_diff`. Disabled by default.
> - [Enabled on GitLab.com and self-managed](https://gitlab.com/gitlab-org/gitlab/-/issues/276918) in GitLab 15.7.
> - [Generally available](https://gitlab.com/gitlab-org/gitlab/-/issues/276918) in GitLab 15.8. Feature flag `display_merge_conflicts_in_diff` removed.
To avoid displaying the changes that are already on target branch in the diff,
we compare the merge request's source branch with HEAD of the target branch.
When there are conflicts between the source and target branch, we show an alert
per conflicted file on the merge request diff:
## Add a comment to a merge request file
> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/123515) in GitLab 16.1 [with a flag](../../../administration/feature_flags.md) named `comment_on_files`. Enabled by default.
> - [Feature flag removed](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/125130) in GitLab 16.2.
You can add comments to a merge request diff file. These comments persist across
rebases and file changes.
To add a comment to a merge request file:
1. On the left sidebar, select **Search or go to** and find your project.
1. Select **Code > Merge requests** and find your merge request.
1. Select **Changes**.
1. In the header for the file you want to comment on, select **Comment** (**{comment}**).
## Add a comment to an image
In merge requests and commit detail views, you can add a comment to an image.
This comment can also be a thread.
1. Hover your mouse over the image.
1. Select the location where you want to comment.
An icon is displayed on the image and a comment field is displayed.