Browser extensions
SwiftCheck
A speed test that answers in the unit your downloads actually use.
- Role
- Sole author — extension and site
- Period
- 2025
- Status
- Live
The problem
Speed tests report megabits per second. Operating systems, browsers and download managers report megabytes per second. The two differ by a factor of eight, so a connection measured at 10 Mbps downloads at 1.25 MB/s — and people reasonably conclude something is broken. Running the test usually also means visiting an ad-heavy site.
The approach
SwiftCheck reports every figure in MB/s, the same unit the file manager uses, and runs from the browser toolbar instead of a website. Throughput is measured with PerformanceResourceTiming — the browser's own network-stack timing — rather than a JavaScript wall clock, so the reading reflects bytes on the wire and is not skewed by script execution.
What it does
MB/s throughout
Real megabytes, matching what the download manager reports: 100 Mbps displays as 12.5.
Adaptive test size
A 256 KB probe estimates the connection first, then the main transfer is sized to roughly three seconds at that speed — accurate on slow links without wasting data on fast ones.
Dynamic dial scale
The speedometer ceiling is set from the probe, so a 1 MB/s connection gets a 0–3 scale with full needle travel instead of a needle pinned near zero.
One outbound host
No analytics, no accounts, no collection. The only host it talks to is Cloudflare's speed endpoint.