Changing default diff direction to "natural" diff order (left is base/original, right is local/modified)

[iloveeclipse]

For many years, Eclipse has used a non‑standard diff order:

• Left: local / modified version
• Right: base / original version

In contrast, almost all modern tools that display code diffs use the opposite convention:

• Left: base / original version
• Right: local / modified version

This “natural” order is what developers typically encounter today - for example in GitHub pull requests or IDEs such as VS Code or IntelliJ IDEA (see for example: https://www.jetbrains.com/help/idea/comparing-file-versions.html).

The historical Eclipse behavior likely originates from the CVS era, when comparisons were framed as local vs. server, and the choice of placing the local version on the left was made at that time. While this may have been reasonable then, today most Eclipse users work primarily with Git and other modern version control systems, where the opposite convention is the norm.

Support for configuring the diff order in Eclipse was added long ago (see Bug 213780: https://bugs.eclipse.org/bugs/show_bug.cgi?id=213780). A proposal to change the default to the natural diff order was later discussed in Bug 501752 (https://bugs.eclipse.org/bugs/show_bug.cgi?id=501752), but it was not completed due to missing test fixes and lack of follow‑up.

Recently, the remaining work was completed (eclipse-platform/eclipse.platform#2566), and starting with Eclipse 4.4 M2, Eclipse uses the common, natural diff order by default. Importantly, users can still switch back to the legacy order if they prefer by a single click and the choice will be persisted.

The button to switch the order is in the compare editor toolbar:

We recognize that some long‑time Eclipse users may find this change disruptive, as they are accustomed to the traditional Eclipse diff layout.

The key question for the community is:

Should Eclipse continue to use its historical diff order by default, or should it align with the natural diff order used by virtually all other modern tools?

We would like to hear the broader community’s opinion on this topic.

This poll is non‑binding and will run until 14 May 2026 (Eclipse 4.4 M3 is scheduled for 15 May 2026).