Low-End Device Performance: The Decisions That Matter
How sites perform on older and cheaper phones with slower processors and less memory.
Marcus Adeyemi
The key figures
- CPU limits
- parsing and executing JavaScript is slower on low-end devices
- Memory
- heavy pages can crash tabs
- Thermal throttling
- sustained work slows devices further
- Field data
- shows the device mix of real users
Why this is worth getting right
JavaScript-heavy pages that feel fine on modern hardware can be unusable on the devices many people actually own.
Do this, not that
Do
- Test on a representative low-end device
- Use CPU throttling in development tools
- Reduce JavaScript payloads
- Check field data for device distribution
- Set performance budgets based on real devices
Don’t
- Testing only on current flagship phones
- Assuming device performance improves for everyone
- Ignoring crash reports on older devices
- Budgets set from lab results alone
When to bring in help
Our advice Bring in help when analytics show high mobile bounce rates.
Where this comes from
- Chrome for Developers — CPU throttling
- web.dev — Performance
The figures and practices above come from the sources listed.
Working on something like this?
We take on Performance & Accessibility work for teams who want it done once, properly. Tell us what you are building and we will tell you honestly whether we are the right studio for it. Start a project.
Where to go next
Spotted something wrong? Report an error on this page. We correct on the page and say what changed.
