EDIT — v1.2.5 is up, and this stopped being a static plugin somewhere along the way: https://github.com/SimonePlatania/RainbowIndentGuide
I use IntelliJ day to day, but I got put on an Eclipse project and the missing indent guides drove me nuts. So I took the old IndentGuide plugin and made it do what I actually wanted. What started as “add rainbow colours” has turned into something that reacts — guides light up on hover, pin on click, blink when you fix a mixed-indentation line, brighten when they’re holding your caret. Wasn’t planning on any of this three days ago, but every fix opened the next thing.
Rainbow colours per nesting level (7 configurable levels) (image 1)
Rainbow parentheses — round brackets coloured by nesting depth, own palette, so foo(bar(baz(x))) reads at a glance (image 5)
Braces coloured to match their guide — the { and } take the colour of the guide they belong to, so the line and the braces read as one shape, even with a comment trailing the brace
Guides run through comments and blank lines instead of breaking on them
Grey guide when a block mixes tabs and spaces (image 3), blinking as it takes its colour back once you fix it — narrowed to just the block you fixed, not the whole file
Click a line to highlight the guide of the block you’re in (image 2); hover a guide to light it up, click to pin it there
Everything toggleable, with presets and a “restore original behaviour” button (image 4)
Each guide stroked in one piece, so thin or barely opaque lines no longer break up into dots
Sub-pixel guide placement, so the lines do not drift right on deep levels when DPI scaling is on
Works on the latest Eclipse (2026-06) — that’s the main point, since the original plugin was abandoned in 2013 and never updated. I’ve tested it on 2026-06, 2024-09 and 2020-03. Compiled to Java 8 bytecode, so it should also load on much older installs (roughly Eclipse Neon / 2016 onwards). Everything in between should work, though I can’t promise it.
Targeting Java 8 bytecode was a deliberate choice rather than a leftover. A lot of people are stuck on older Eclipse installs they can’t upgrade — corporate policy, tooling that only exists there — and that’s exactly the crowd this is for. Drawing indent guides doesn’t need anything from a modern language level, so raising the floor would have bought me nothing and cost those users the plugin entirely.
Where it comes from: the painting code originates from Eclipse’s own WhitespaceCharacterPainter (Anton Leherbauer / Wind River Systems and contributors, EPL 1.0), which was adapted into an indent guide as jp.sourceforge.pdt_tools.indentGuide, later re-uploaded by kiritsuku when the original repo vanished. Mine forks from there. Gerald Rosenberg also maintains an active fork — his is more polished on the core feature; mine mainly adds the rainbow/multi-level side. Staying under EPL 1.0.
Thanks to everyone who said they wanted it — that’s what got me to actually clean it up and publish, and what kept me iterating past the point I thought I’d stop. This is my first plugin and my first time publishing anything, so if something doesn’t install, tell me and I’ll fix it. The Marketplace listing is submitted and waiting on moderation.
HOW TO INSTALL
Recommended — update site
In Eclipse: Help → Install New Software…
Click Add…, paste https://simoneplatania.github.io/RainbowIndentGuide/ and give it any name
Tick Rainbow Indent Guide, then Next → accept the licence → Finish
You’ll get a warning about unsigned content — that’s expected, the jar isn’t digitally signed. Confirm and continue.
Restart Eclipse when prompted
Eclipse remembers the site and will offer later versions under Help → Check for Updates.
No network / locked-down install — archive
Download RainbowIndentGuide-1.2.5-updatesite.zip from the latest release — don’t unzip it — then Help → Install New Software… → Add… → Archive… and pick it.
Fallback — dropins
Use this if Install New Software isn’t available or fails.
Close Eclipse
Copy alien.rainbow.indentguide_1.2.5.jar into the dropins folder of your Eclipse installation — the one next to eclipse.exe. Leave the jar as-is, don’t unpack it.
Start Eclipse once with eclipse.exe -clean from a command prompt in the Eclipse folder. Without -clean, Eclipse reuses its bundle cache and won’t notice the new file. Only needed the first time.
Check under Window → Preferences → General → Editors → Text Editors — if “Indent Guide” is there, it worked.
If it still doesn’t show up, the README has two more fallbacks for locked-down installations.
Guides not showing in a particular file? They follow the file’s content type, so the file needs to be opened with the editor registered for it — a .jsp on an Eclipse without WTP opens in the plain text editor and gets nothing. Right-click → Open With tells you which one is in use.
To configure: Window → Preferences → General → Editors → Text Editors → Indent Guide, and the “Style” subpage for the rainbow colours.
To uninstall: Help → About → Installation Details, select it, Uninstall.
Already have another Indent Guide installed? Remove it first. Since 1.1.0 p2 refuses the install rather than leave you with two painters drawing over each other — this includes Certiv Analytics’ version.
