Linux

PSA no matter how light your distro, any modern app or webpage will use all that power

I usually go with Xfce.

That's fast enough to run the latest Linux Mint with Cinnamon. I have two laptops with the exact same cpu speed (passmark score) and 4 GB of ram. With 2 GB swap file you will be in business.

I'm running Kubuntu on less than that on a desktop and it works just fine.

If you are still using X, get Fluxbox, very lightweight, requires some config, but that is fairly easy.

LXQt, XFCE Or a window manager, they’re all lightweight.

Technically not a DE, but I like plain openbox.

If you don’t need a full desktop environment, check-out IceWM.

I recently checked-out Trinity ( essentially KDE 3 modernized ) and was surprised how decent it was. I used it in Q4OS but it may be available in your distro.

Its fairly difficult to find "up-to-date" performance / RAM comparisons of Linux Desktop environments, but here's a decent one from 2019 comparing memory usage of different Ubuntu flavors.

The most surprising thing is that despite KDE Plasma's reputation as being more ram-hungry, it actually used less ram than XFCE, meaning its developers have been making performance a focus.

• the big guns: Gnome or Plasma
• the middle tier: Xfce or LXQt
• the lightweights: tiling window managers (and there’s a LOT to choose from)
• the alternative crowd: Mate, Cinnamon, Regolith

KDE plasma. From my experience it uses less resources than lxqt and xfce and works out of the box while lxqt and xfce required extra work to get wifi, screen brightness controls and audio working. I can have 10+ tabs in a chromium based browser open without lag on an old laptop with 2GB ram and 1.33 - 1.83GHz 4 core intel atom from 10 years ago.

I would go mx linux fluxbox

A window manager like i3 or Openbox. If you are curious what that's like, then try out Bunsenlab Linux. (XFWM4 is also a great choice, but it requires some know how to properly rip out the rest of Xfce, like the relatively heavy desktop and the panel)

Xfce, LXQt or just install JWM and enjoy the 30 Mb idle RAM usage

LXQt, XFCE, Maté, TDE. Any of them will do. Which you choose depends on personal preference and how large an ecosystem you want—LXQt has only a few basic applications, TDE has pretty much everything that was in KDE3, the others are somewhere in between.

You could try Niri. I have tested it with a ~10 year old notebook with a 1st gen Core i5 cpu.

But, even newest Gnome runs smooth on this machine.

I love OB with tint2 and conky , no de needed.

Your biggest problem is going to be the 4 GB of RAM. Saving a few hundred megs on the DE will help but not much. If you run a web browser ( and I cannot imagine using a computer without one ) that RAM is going to fill up fast.

Honestly, I would use a 32 bit distro on that hardware.

Q4OS with Trinity, Antix, Adelie, and DSL are all pretty decent options.

Xfce

Does Xfce count as light? It's got plenty of features. Should fit in 4gb well enough though.

There are many options, but I'd say on those specs anything will run more or less fine with some tweaks/settings.

Personally I would go with KDE Plasma, because I feel most comfortable with it. It can be pretty light on system ressources when configured properly. Disable all the visual stuff (animations, blur, anti aliasing) and some of it's background modules (baloo and some other stuff that you personally don't need).

But you should take the one you are familiar with and find out how you can tweak it to be more light. Cheers

Moksha Desktop environment Bodhi Linux

Probably lxqt. https://lxqt-project.org/ Very lightweight yet a full-on DE (minus bells and whistles). Found on most Linux distros repositories.

Does not answer your question, and someone already mentioned it in a thread, but don't forget zram when only 4GBs are available.

XFCE or LxQT but i have a preference for XFCE if it is for normal use.

For something with that little memory, I would use a minimal window manager; you'll want every megabyte of memory if you want to have any chance at running something like a javascript-capable browser without constantly hammering swap. fvwm, cwm, jwm, and ratpoison are all small window managers I enjoy; but do your own research into what window manager is the best for you.

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I have a thumb drive with Mint Mate installed on it and it runs fine on a 4gb i5 - 3rd gen.