4K Video Playback Test
Find out if this device can really play 4K or 8K video smoothly. The test creates a high resolution clip in your browser, measures how fast it decodes, then plays it while counting every dropped frame.
Last updated:
| Video | Decode speed | Playback FPS | Dropped | Result |
|---|
How to use the 4K Video Playback Test
- Choose the resolution, frame rate and codec. The default is 4K at 30 fps in VP9.
- Press Start test: the page creates a 4 second clip, measures decode speed, then plays it on a loop.
- Keep the tab in front until the result appears; switching tabs pauses video and spoils the measurement.
- Read the result: decode speed should be well above the frame rate and dropped frames close to zero.
- Press Run 1080p, 4K and 8K to compare, or Play your own video to test a real file.
What each number means
| Measurement | How it is measured | Good result |
|---|---|---|
| Decode speed | All frames of the clip are decoded twice with WebCodecs VideoDecoder as fast as possible; frames ÷ seconds | At least 1.1× the frame rate; 2× or more leaves headroom |
| Playback FPS | Frames presented to the screen, counted with requestVideoFrameCallback, divided by the playback time | Equal to the video frame rate, or your refresh rate if that is lower |
| Dropped frames | droppedVideoFrames ÷ totalVideoFrames from getVideoPlaybackQuality during playback | 0 to 1% of frames |
How much work each resolution is
| Resolution | Pixels per frame | Pixels per second at 30 fps | Pixels per second at 60 fps | Typical streaming bitrate (SDR) |
|---|---|---|---|---|
| 1080p (1920 × 1080) | 2.07 million | 62 million | 124 million | 5 to 12 Mbps |
| 1440p (2560 × 1440) | 3.69 million | 111 million | 221 million | 9 to 18 Mbps |
| 4K UHD (3840 × 2160) | 8.29 million | 249 million | 498 million | 15 to 45 Mbps |
| 8K UHD (7680 × 4320) | 33.2 million | 995 million | 1.99 billion | 50 to 100+ Mbps |
Bitrate ranges are typical figures used by streaming services and encoder presets; actual values vary by codec and content. The test clips use 8, 14, 25 and 60 Mbps targets for 1080p, 1440p, 4K and 8K, raised by half at 60 fps.
Tips for smooth high resolution video
- Turn on hardware acceleration in the browser settings and keep the graphics driver up to date.
- Pick a codec your GPU decodes in hardware: VP9 and H.264 almost everywhere, AV1 only on recent hardware.
- Plug in laptops and choose a performance power mode; battery saving can halve decode speed.
- A 60 Hz screen cannot show more than 60 frames per second, so a 120 fps video always looks like 60 fps on it.
- If the clip plays smoothly but a streaming site stutters, the cause is usually network speed or a different codec on the site.
Frequently asked questions
How does the 4K playback test work?
It draws a detailed animated clip at the chosen resolution, encodes it with the WebCodecs VideoEncoder and packs it into a WebM file, all inside your browser. It then decodes the clip as fast as possible to measure decode speed, and plays it in a normal video element while reading getVideoPlaybackQuality for dropped frames and requestVideoFrameCallback for the frames actually shown.
What counts as smooth playback?
The test calls playback smooth when no more than 1% of frames are dropped, at least 93% of the expected frame rate reaches the screen, and decoding runs at least 10% faster than the video's frame rate. Up to 3% dropped frames is shown as mostly smooth. The expected frame rate is the clip's frame rate or your refresh rate, whichever is lower.
Why is 8K not smooth or not supported?
8K has four times the pixels of 4K, so it needs a hardware decoder that supports 8K, which only recent GPUs and chips have. Without one the CPU has to decode about 33 million pixels per frame, which is too slow on most computers. Some browsers also cannot encode 8K clips at all; the test then says so.
Is decode speed the same as hardware acceleration?
Not exactly. A decode speed many times the frame rate usually means a hardware decoder is used. A speed close to the frame rate with high CPU use suggests software decoding. The video codec support checker shows the browser's own power efficient flag, which is the closest a web page can get to confirming hardware decoding.
Why does my real 4K video stutter when this test is smooth?
Real videos may use another codec, such as HEVC or AV1, a higher bitrate, HDR or a higher frame rate. Streaming also depends on your internet speed. Use Play your own video with the actual file, or check the codec with the codec support checker.
Does the test upload or download any video?
No. The test clip is generated locally and your own files are played straight from your device. Nothing leaves your browser.
Why do results change between runs?
Power saving, background apps, browser updates and laptop thermals change how fast the CPU and GPU run. Plug in laptops, close other apps and run the test twice for a reliable reading.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.