Why speed is such an easy lever to pull
Unlike color grading, cropping, or adding effects, changing playback speed doesn't require judgment calls about how something should look — it's a single number, and the visual effect is immediate and predictable. A tutorial that drags at normal speed becomes watchable at 1.5x, and a mundane process shot at normal speed becomes an engaging time-lapse at 4x or 8x.
This is why speed adjustment is one of the most commonly requested simple edits — it fixes a pacing problem without needing to re-shoot, re-cut, or make any creative decisions beyond picking a number.
What happens to audio when you change speed
Speed changes affect the audio track too — speeding up raises pitch and shortens duration, slowing down lowers pitch and stretches it out, exactly like an old vinyl record played at the wrong speed. For any clip with dialogue or music, this quickly starts sounding unnatural even at modest speed changes, which is why many speed-change tools offer to mute audio entirely as an option, especially for large speed multipliers.
For content where the sound doesn't matter (background loops, silent time-lapses, footage that will get new music added afterward), muting sidesteps this problem entirely rather than trying to fix distorted pitch after the fact.
Slow motion needs enough source frame rate to look smooth
Slowing footage down doesn't create new frames out of nothing — it stretches the existing frames over more time, so footage shot at a standard 30fps slowed to half speed effectively becomes a smoother-looking 15fps-equivalent motion, which can look choppy in fast action. True smooth slow-motion needs footage originally shot at a high frame rate (60fps, 120fps, or higher) specifically so there's enough real frame data to stretch out convincingly.
If your source footage was shot at a standard frame rate and you slow it down significantly, expect some visible choppiness in fast-moving subjects — that's a limitation of the source material, not something the speed tool is doing wrong.
Common speed multipliers and what they're good for
1.25x-1.5x is the sweet spot for tightening pacing on talking-head content, tutorials, or lectures without making speech sound obviously sped up. 0.5x-0.75x works well for emphasizing a specific action or moment without going full dramatic slow-motion. Beyond 2x in either direction starts to feel like a distinct stylistic choice — comedic fast-forward or a hyperlapse effect — rather than a subtle pacing fix.
There's no universally correct speed; it depends entirely on what you're trying to achieve, and it's worth previewing a short section before committing to a speed change across an entire longer clip.