Javascript animations in Firefox ESR very slow/jittery

Troubleshooting
1

Creating a bug report/issue

I have searched the existing open and closed issues

Required Information

  • DietPi version:
    G_DIETPI_VERSION_CORE=9
    G_DIETPI_VERSION_SUB=15
    G_DIETPI_VERSION_RC=2
    G_GITBRANCH=‘master’
    G_GITOWNER=‘MichaIng’
  • Distro version: bookworm
  • Kernel version: Linux tvscreen 6.12.34+rpt-rpi-v8 #1 SMP PREEMPT Debian 1:6.12.34-1+rpt1~bookworm (2025-06-26) aarch64 GNU/Linux
  • Architecture: arm64
  • SBC model: RPi Zero 2 W (aarch64)
  • Power supply used: Official Raspberry Pi 12.5W Micro USB Power Supply
  • SD card used: Official Raspberry Pi 32GB A2-Class micro SD card

Additional Information (if applicable)

  • Software title: Firefox ESR
  • Was the software title installed freshly or updated/migrated? fresh
  • Can this issue be replicated on a fresh installation of DietPi? i don’t know/this is a fresh install

Steps to reproduce

  1. run this custom autostart script: xinit /usr/bin/firefox-esr –height 1080 –width 1920 –kiosk –private http://my.website/ -- -nocursor

Expected behaviour

  • website loads and javascript animations are smooth

Actual behaviour

  • javascript animations are extremely slow and jittery, affecting the FPS of the whole page

Extra details

i know i’m probably pushing the limits of what an rpi0 can do, but i really only need it to show one web page and function as a sign; not to be interacted with at all.

  • i’ve tried increasing the swap file to 1GB but it doesn’t seem to help much. free -m output is as follows:
    total used free shared buff/cache available Mem: 384 214 36 21 165 170 Swap: 1023 180 843
  • the GPU/RAM split is set to 96. tried increasing it to 128 but it didn’t seem to help
  • set the CPU governer to ondemand; not sure how much that helped
  • tried setting gfx.webrender.all to true in /etc/firefox-esr/firefox-esr.js but that made things worse. firefox would freeze and CPU temperature spiked
  • CPU runs consistently around/just below 50°C at 1000MHz
  • i did originally try to use the built-in autostart chromium script, but it wouldn’t reliably load the javascript elements, so i wrote my own script with firefox