BrowserTools

Internet Speed Test

Download, upload, ping and jitter

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-09-01
Free No sign-up Uses a third-party API

This measurement is a genuine network transfer. The page downloads JavaScript files from the jsDelivr CDN and posts filler blocks to Cloudflare's public speed-test endpoint, so it consumes real bandwidth and shows up against any data allowance. Nothing you type is involved and no account is used, but the run itself moves a lot of data.

What is Internet Speed Test?

The test runs three phases and reports measured figures rather than a decorative dial. Ping comes first: six small requests to a jsDelivr package.json, each carrying a random query string so nothing is served from cache, giving a median round trip and the mean gap between adjacent samples as jitter. Download runs for six seconds, streaming known-size JavaScript files out of the jsDelivr CDN and counting the bytes that actually arrive. Upload posts 512 KB blocks to Cloudflare's public speed-test endpoint for the same six seconds, counting only requests the browser accepted. If that endpoint refuses a cross-origin POST, the page reports upload as not measurable instead of printing a number it never obtained. A closing panel turns the download and ping figures into a sentence about streaming and calls.

Measure your real download speed, upload speed, ping and jitter with a browser-based test. No Flash, no app — just a direct measurement between your browser and the nearest test node.

Runs In Your Browser

Runs in your browser, but this tool contacts a third-party service to do its job. The overview above says exactly what is sent.

Step-by-Step

How to use Internet Speed Test

1

Press Start speed test. Ping is measured first, with six cache-busted requests to a jsDelivr package.json.

2

Watch the download phase run: for six seconds the page streams JavaScript files from the jsDelivr CDN and tallies the bytes received.

3

The upload phase then posts 512 KB blocks to https://speed.cloudflare.com/__up, counting only the requests that complete.

4

Read the four tiles — Download, Upload, Ping (median) and Jitter — followed by the panel that interprets the download and ping values.

Key Capabilities
  • Ping is the median of six cache-busted requests rather than a single round trip, and jitter is the mean absolute difference between adjacent samples.
  • Download is computed from bytes streamed out of a live response body, not from a Content-Length header or a figure the CDN reports.
  • Upload counts only POSTs the browser accepted; if the endpoint blocks cross-origin traffic the tile reads Not measurable rather than inventing a number.
  • A Cancel button aborts the run through an AbortController, so a test can be stopped without sitting through the remaining phase.
Common Use Cases
  • A support engineer asks a customer reporting slow page loads to read out ping and jitter before anyone changes a router setting.
  • A developer separates a bandwidth problem from a latency problem by seeing whether download is healthy while ping is high.
  • Someone on hotel Wi-Fi finds out whether the bottleneck is the network or their own laptop by comparing this with their usual home result.
Clear Answers

Frequently Asked Questions

Why is this lower than the speed my provider advertises?
Advertised figures are measured on a wired line inside the provider's own lab, usually to a server a few kilometres away. This runs in a browser over Wi-Fi on a path crossing several networks, sharing capacity with anything else on the same line. Landing within roughly half the advertised number is ordinary.
The upload tile says not measurable. Is something broken?
The upload phase needs an endpoint that permits cross-origin POST requests. When every attempt is rejected by the browser there is no measurement to report, so the page says so rather than printing a partial figure. Ping and download are unaffected and still run.
How much data does one run use?
The download phase lasts six seconds at whatever rate the line sustains, which on a fast connection can reach a few hundred megabytes, and the upload phase adds a few tens of megabytes. Press Cancel or close the tab if the allowance matters.
Can I run two tests at the same time?
You can, but the phases will compete for the same bandwidth and both sets of numbers will be wrong. Let one finish before starting the next, and close other downloads and video calls first.