Check your download, upload, ping & jitter in seconds — free, no app.
Check your internet speed in one click. Check.Fast is a free internet speed test that measures your download speed, upload speed and ping in seconds — and shows your ISP, IP address and location. No app, no sign-up, works on any device. Run a quick broadband speed test, WiFi speed test or mobile data speed test from the same page.
Unlike a basic bandwidth test, Check.Fast also measures the things that decide how your connection feels in real use: jitter, bufferbloat, packet loss and connection stability. You get a clear A–F grade and a plain-English verdict, so you know instantly whether your internet is good for gaming, 4K streaming, video calls and working from home. Want to go deeper? Read our Internet Speed Test Guide for help fixing slow WiFi, lowering ping and getting the most from your plan.
Check.Fast is built to be fast, honest and private. There are no ads, no account, and no app to install — just open the page and tap GO. The test runs entirely in your browser against a global network that automatically routes to a server near you, the same approach used by the major speed tests. It works on iPhone, Android, Windows, Mac and any modern browser, and it keeps a private history of your results on your device so you can compare over time.
Tap the GO button above. The test first checks your ping (response time), then measures download and upload throughput against a nearby server. For the most accurate speed test result, close other apps, pause downloads, and test over a wired connection or close to your WiFi router.
For a typical household, 100 Mbps or more handles 4K streaming, video calls and gaming across several devices at once. What matters just as much is low, stable ping and jitter — that's what keeps calls clear and games lag-free. Speeds are shown in Kbps, Mbps or Gbps depending on your connection.
Download speed is how fast data reaches you — it affects streaming, browsing and downloads. Upload speed is how fast you send data out — it affects video calls, cloud backups and live streaming. Most home plans give you far more download than upload.
The most common causes of slow internet are WiFi distance or interference, an overloaded or outdated router, too many connected devices, or ISP throttling. Quick fixes: switch to the 5GHz WiFi band, reboot your modem and router, move closer to the router, and run the speed test again to compare.
Yes — Check.Fast is completely free, with no app and no sign-up required.
It measures real throughput using parallel transfers to a nearby server. Results depend on your device, WiFi, and current network traffic, so test a couple of times for a clear picture.
Yes. Check.Fast runs in any modern browser on phones, tablets, laptops and desktops — no app to install.
Ping is the round-trip response time in milliseconds. Lower is better — under 20 ms is excellent for gaming and video calls.
Connect to your WiFi, open Check.Fast and tap GO. Test next to the router and again in the room where it feels slow — the difference tells you if WiFi coverage is the problem rather than your internet plan.
For online gaming, ping under 50 ms and stable jitter matter most. 15–25 Mbps download and 5 Mbps upload are plenty; low latency beats raw speed for a lag-free experience.
Netflix recommends about 3 Mbps for SD, 5 Mbps for HD and 15–25 Mbps for 4K Ultra HD per stream. For several devices streaming at once, aim for 50–100 Mbps or more.
WiFi distance and interference, an old router, peak-hour congestion, background downloads, VPNs, or ISP throttling can all reduce real-world speed below your plan. Test over WiFi and over Ethernet to see how much WiFi is costing you.
Mbps is megabits per second (how ISPs measure speed); MBps is megabytes per second (how files download). Divide Mbps by 8 to get MBps — so 100 Mbps ≈ 12.5 MBps download speed.
Check.Fast automatically detects and displays your public IP address, internet service provider (ISP) and approximate location after the page loads — shown below the speed gauge.
Jitter is the variation in your ping over time. High jitter causes choppy video calls and lag spikes in games even when your speed looks fine. Under 10 ms is good; under 5 ms is excellent.
Test whenever your connection feels slow, after changing routers or plans, and at different times of day. Comparing results helps you spot peak-hour slowdowns or ISP throttling.
Bufferbloat is extra delay (latency) that builds up when your connection is busy — for example while uploading a file or streaming in 4K. Oversized buffers in your router or modem hold packets in a queue, so your ping spikes under load even when your speed looks fine. Check.Fast measures it by comparing your idle ping to your ping during the download and gives it a grade from A (excellent) to F (severe). High bufferbloat causes lag spikes in games, frozen video calls, and slow web pages while something is downloading. The fix is enabling Smart Queue Management (SQM, also called QoS or fq_codel) on your router, upgrading to a modern router, or replacing an old modem. Read our full bufferbloat guide →
Loaded latency is your ping measured while the connection is fully busy (under load), as opposed to idle ping measured when nothing else is happening. It is one of the most important real-world metrics because it predicts how your connection behaves during actual use — gaming while someone streams, or a video call while files sync to the cloud. A big gap between idle ping and loaded latency means bufferbloat. Lower loaded latency (under 100 ms) keeps games, calls and browsing responsive even when the connection is working hard.
Packet loss is the percentage of data packets that never reach their destination and have to be re-sent. Even small amounts (1–2%) cause stutter in video calls, rubber-banding in online games, and buffering while streaming. Common causes include WiFi interference, a weak or distant signal, a faulty cable or modem, an overloaded connection, or congestion at your ISP. Anything above 0% under load is worth investigating; a wired Ethernet connection and a reboot of your modem and router often fix it.
Connection stability measures how consistent your latency and throughput stay during the test — shown as a percentage where higher is better. A stable connection (90%+) delivers smooth, predictable performance, which matters more than peak speed for video calls, gaming and live streaming. Low stability means your speed and ping are fluctuating, usually due to WiFi interference, network congestion, an overloaded router, or an unreliable line. Switching to 5GHz WiFi, moving closer to the router, or using Ethernet improves stability.
WiFi signals weaken with distance, walls and interference from other networks and devices, so they almost always test slower than a direct Ethernet cable. For the fastest, most stable result, plug your device straight into the router. If WiFi is much slower, try the 5GHz band, move closer to the router, or consider a mesh system for better coverage.
Yes, usually a little. A VPN encrypts your traffic and routes it through a remote server, which adds some overhead and distance, so download and upload speeds often drop and ping rises. The slowdown depends on the VPN provider, the server location and your base connection. To measure your true ISP speed, run the test with the VPN turned off.
For competitive online gaming, aim for a ping under 50 ms — under 20 ms is excellent. Anything above 100 ms feels laggy. Low, stable ping and low jitter matter far more than raw download speed for a smooth gaming experience. A wired Ethernet connection and enabling QoS on your router help keep ping low.
Real internet speed naturally fluctuates with network congestion, the time of day, WiFi conditions, the test server, and what else is using your connection. Small differences between tests are normal. For a reliable picture, run the test two or three times, ideally wired, and compare the results rather than relying on a single number.
For comfortable remote work with video calls, 25–50 Mbps download and 10 Mbps upload is plenty for one person. If several people stream, call and upload at once, aim for 100 Mbps or more. Upload speed and low, stable latency matter a lot for video calls — check your upload and bufferbloat grade, not just download.
Restart your modem and router, move closer to the router or use the 5GHz band, switch heavy devices to a wired Ethernet connection, remove unused devices from the network, update your router firmware, and enable QoS/SQM to control bufferbloat. If speeds are still far below your plan, contact your ISP — the line or equipment may need attention. See 15 ways to speed up your WiFi →
Yes — 200 Mbps comfortably handles 4K streaming on several devices, online gaming, and multiple video calls at once for most households. Only very large families, heavy 4K-everywhere homes, or people moving huge files regularly need 500 Mbps or gigabit. More on what 200 Mbps can do →
Open your browser (Safari, Chrome or any other), go to check.fast and tap GO — no app required. Test next to your router for your best WiFi reading, then in other rooms to find dead zones, and compare WiFi against mobile data. Full phone speed test guide →
A good speed test is accurate when run correctly — wired, on a modern device, with other apps closed. WiFi, old hardware and background downloads all lower the reading. Check.Fast uses adaptive multi-stream measurement and shows a confidence indicator so you know how reliable each result is. How speed test accuracy works →
How your speed ramped during the test — a steady line means a stable connection.