About Redline

Most performance tooling measures servers. Load generators such as k6, JMeter, Locust and Artillery answer one question well: how many requests per second can the backend absorb before it degrades. That leaves a blind spot. A page can be served in 40 milliseconds and still feel broken on the phone in someone's hand, because the bottleneck is the device — a saturated CPU, a throttled GPU, memory pressure, or layout work that blocks the main thread.

Redline measures that side of the equation. It runs a battery of synthetic workloads in the visitor's own browser — integer and floating point CPU passes, allocation and garbage-collection pressure, layout and paint churn, GPU shading, and network round trips — then combines the results into a single comparable score alongside a per-subsystem breakdown.

Every benchmark executes locally. Nothing about your machine is uploaded unless you choose to save a run to your account or publish a shareable report. The scoring model weighs each subsystem against budgets derived from device classes we observe, so a mid-range Android and a workstation are graded against realistic expectations rather than a single absolute bar.

Alongside the raw numbers, Redline produces a plain-language summary that explains what the result means for an ordinary user, and — on paid plans — a deeper written analysis generated by a language model from the same measurements.

Redline is built and operated by Redline Labs, a small independent software team. We are not affiliated with, sponsored by, or endorsed by any of the tools we compare ourselves against. Product decisions, benchmark weightings and written guidance are our own.

You can reach a human at contact@redlinetesting.com, or use the contact page.

The public tool is free and always will be. It is paid for two ways: advertising shown to visitors on the free tier, and a paid Team plan for companies that need cloud run history, deep AI analysis, shareable reports, CI budget checks and an ad-free experience.

Advertising is loaded only after consent where the law requires it, and never for paying subscribers. What we collect and who processes it is set out in the privacy notice and the subprocessor list.

Comparison pages, guidance and benchmark interpretation are written by us and are not paid placements. Advertising is clearly labelled as such and is kept separate from editorial content and from measurement results. No advertiser can influence a score.