インターネット速度テスト
Check download speed, upload availability, latency, and jitter with safe browser network requests.
Run a compact same-origin test and keep partial results when a metric is unavailable.
Options
Auto mode is balanced by default. Disable metrics when you only need a quick signal.
Download and latency use cache-busted same-origin requests. Upload is skipped unless a project endpoint is configured.
Browser network details unavailable.
Diagnostics
Connection health, test details, and practical quality hints.
Results will appear here after a test.
What is Internet Speed Test?
Internet Speed Test is a browser-based network diagnostic tool for checking whether your internet, Wi-Fi, VPN, or current browser route feels slow, unstable, or down. It measures download speed, latency, and jitter with safe cache-busted requests from the browser, then reports upload as unavailable unless a project-approved upload endpoint is configured.
How to use
1. Open the tool and click Start Test. 2. Keep the default Balanced mode for a quick everyday check, or switch to Quick or Thorough. 3. Disable download, upload, latency, or jitter when you only need one signal. 4. Review the connection health, diagnostics, and practical hints for calls, gaming, browsing, and uploads. 5. Copy the plain text summary, download JSON, restart the test, or clear the result.
What the metrics mean
Download speed estimates how quickly this browser can receive data and is shown in Mbps. Upload speed estimates outbound transfer speed when a safe upload endpoint exists. Latency is the request round-trip delay in milliseconds. Jitter is the variation between latency samples, which matters for video calls, voice calls, gaming, remote desktops, and other real-time work.
When to use it
Use this tool when Wi-Fi feels slow, video calls lag, file uploads stall, online games feel delayed, CI dashboards stop loading, or you want a quick network snapshot before reporting a bug. Developers can also use it to separate app performance problems from local network instability.
Connection health guide
Excellent means download is at least 50 Mbps with latency below 50 ms. Good means download is at least 20 Mbps with latency below 80 ms. Fair means download is at least 5 Mbps. Poor is reported for very slow download or latency above 150 ms. Unstable is reported when jitter is above 30 ms because real-time traffic may fluctuate.
Privacy and safety
No manual input is required, no user files are uploaded, and the default tests use same-origin browser requests with cache-busting. The upload test is intentionally skipped unless the application provides a safe endpoint that accepts generated disposable bytes.
Limitations
Browser-based measurements are approximate. VPNs, proxies, CDN routing, browser cache, device load, power saving mode, local Wi-Fi congestion, and server distance can all affect results. Same-origin download tests estimate the route to CodingTool.dev, not every website or every speed-test provider. Upload speed is not faked when no reliable endpoint is available.
Technical Details
Edge Cases & Tricky Inputs
- •Upload speed is skipped when the project does not expose a safe upload endpoint.
- •VPNs, proxies, captive portals, and browser extensions can change measured latency or throughput.
- •Browser cache and CDN routing can make repeated tests vary.
Performance & Processing
- •Quick mode runs fewer samples; Thorough mode runs more cache-busted requests for a steadier estimate.
- •Latency samples are averaged after trimming obvious outliers when enough samples are available.
Developer Notes
- •The tool uses browser fetch with AbortController and per-request timeouts.
- •Default download and latency checks use same-origin resources to avoid third-party endpoints.
Known Limitations
- •Browser-based speed tests are approximate and measure the route from this browser to the configured endpoint.
- •No upload number is displayed unless a reliable endpoint accepts generated disposable bytes.
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