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What is frame rate (fps)?

In one sentence: How many still pictures a video shows each second (fps). More frames look smoother but take more space.

A little more

Video is a fast flip-book of still pictures. The frame rate is how many pictures are shown each second, written as fps (frames per second). Films are usually 24 fps, TV and most phone video 25 or 30 fps, and smooth sport or game footage 60 fps.

More frames mean smoother motion, but more pictures to store, so 60 fps files are bigger than 30 fps ones, usually by about half rather than double, because each frame is very like the one before and the codec only stores what changed. Video calls drop their frame rate when the connection gets tight, which is why people sometimes look jerky before they look blurry.

See it in action

  1. BonusWhy does a game judder when it can't keep up?A screen is a flip book with a thumb that turns the page on a steady beat, and the game is an artist drawing the pages.9 min · interactive
  2. BonusWhy does a video call go blurry when the connection is slow?Dial a pretend video call's bandwidth thinner, spend a tiny 10-bit budget on eyes vs mouth vs wallpaper to still read a facial expression, then reveal the clear face.7 min · interactive
  3. BonusWhy does a video go blurry, then sharp?You press play and the picture is smudgy for a second, then it snaps sharp.8 min · interactive
  4. 14How can lots of people play the same game together?Share a pretend park with friends in other houses: every move is a message to a shared world on a server.7 min · interactive
  5. BonusWhat happens when you squish a video too much?Squish a real (tiny) picture the way phones squish video: watch thin whiskers crumble first, then 8x8 blocks appear, then a splat.10 min · interactive
  6. BonusHow does a game controller talk to a console?Your controller fires tiny paper darts at the console hundreds of times a second, each one a snapshot of every button and stick.8 min · interactive

Do it for real

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Related words

  • Codec The recipe a device uses to squeeze video or sound into a small file and unpack it to play, such as H.264, HEVC or AV1.
  • Bitrate How many bits a stream sends each second. A lower bitrate means a video call must use bigger blocks, fewer pictures, or freeze.
  • Resolution How many pixels a picture or screen has, such as 1920 by 1080; more pixels can show finer detail.
  • Input lag The delay between pressing a button and seeing the result on screen, made of the controller, the connection, the game's frames and the screen added together.
  • Refresh rate How many times a second a screen redraws its picture, such as 60, 120 or 144 times (Hz); more redraws look smoother if the game keeps up.
  • V-Sync Making a game hand new pictures to the screen only between redraws, which stops tearing but can add judder and a little delay.
  • HDR (high dynamic range) A way of describing pictures with much brighter highlights, deeper shadows and more colours than ordinary video; the screen then squeezes it into what it can actually show.

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