How to Change Video Speed Online: Speed Up, Slow Down and Ramp a Clip in Your Browser

Most videos have a stretch that drags and a moment that deserves more time. Changing speed lets you get through the first and linger on the second without cutting anything out.

I'm Fred Abila, and I build Vidmoat, a hosted AI video editor. You get a real multi-track timeline in the browser, plus a chat with an agent that edits that same timeline for you, so you can describe a change in plain words and then adjust it by hand. The same projects open in the iPhone, Android, Mac and Windows apps (vidmoat.com/download), and you can send a clip to @vidmoat_bot on Telegram. Here is how I change video speed in it, step by step.

Two kinds of speed change

It helps to separate these before you touch anything:

• A constant speed change. The whole clip plays faster or slower, evenly. Good for a time-lapse feel or gentle slow motion.
• A speed ramp. The speed changes inside one clip: normal, then slow, then back to normal, or slow into a fast whip. This is the version that looks deliberate. Vidmoat supports it with keyframes, which is the same idea as keyframing scale or position, applied to speed.

Before you start: check your footage

Slow motion has one honest limit. When you slow a clip down, Vidmoat repeats source frames; it doesn't invent new ones with optical flow. A clip recorded at a higher frame rate gives you more real frames to stretch, so it looks smoother when slowed. A clip recorded at a low frame rate will look steppier the more you slow it. Keep that in mind before planning a dramatic crawl on standard-speed footage.

How to change video speed online, step by step

Step 1: Upload your clip and put it on the timeline

Sign in at vidmoat.com and start a new project. In the Media Library tab, use Upload / drop media or drag your file onto the panel, then drag it onto a video track or double-click it to drop it at the playhead. Let any UPLOADING badge clear before you close the tab.

Step 2: Isolate the part you want to change

If you want the whole clip changed, skip ahead. Otherwise put the playhead where the change should start, press B to split, and do the same where it should end. Each section is now its own clip. Splitting is covered in How to Trim and Cut a Video Online.

Turn Snap on so clip edges stick to the playhead, to markers and to other clips, with no tiny gaps between sections.

Step 3: Open Playback Speed

Select the clip. In the Inspector on the right, open the A/V tab and find Playback Speed. The range goes from 0.05x up to 10x, which is wide enough for a near-freeze or a very fast time-lapse. Vidmoat recalculates the media timing for you when speed changes.

Pick a value and play it back. As a starting point, 2x to 4x reads as clearly sped up without becoming a blur, and around half speed reads as slow motion rather than a glitch. Those are my habits, not rules.

Step 4: Ramp the speed with keyframes

For a ramp, add speed keyframes inside the clip where the change should start and where it should end. A typical pattern:

• Normal speed through the setup.
• A keyframe where the interesting moment begins, easing down into slow motion.
• A keyframe after it, bringing the speed back up.

For a product reveal, slow down as the product comes into view, then accelerate into the next shot. For action, put the slow section around what you want people to notice. Play the preview and adjust until it feels like part of the motion rather than a switch being flipped.

Vidmoat also has one-click Reverse and Freeze frame for clips where you want those instead.

Step 5: Land the ramp on a beat

If your video has music, a ramp feels better when it lines up with the beat. Press M to drop a marker at the playhead where a beat falls, and Snap will pull clip edges to it. Automatic beat markers are covered in How to Add Music to a Video Online.

Step 6: Deal with the sound

A speed change affects the clip's audio too, so listen with the sound on before you export. Use the A/V tab for volume and fades, or mute the clip. For a sped-up section I usually drop the original audio and lay music under it.

Step 7: Let the agent do it instead (optional)

If you'd rather describe it, press Cmd/Ctrl+K to open the AI console, or select a clip and click AI Prompt in its action bar to point the agent at that clip. Try something like: "Time-remap this clip: fast-forward through the setup, slow down to 20 percent speed at the moment of the jump, and return to normal speed on the downbeat." The agent reads the timeline and makes the edits, and you can still adjust them by hand. Agent runs use AI credits; manual editing never does.

Step 8: Preview and export

The J, K and L keys speed up the preview, up to 8x, without changing the clip's speed. When it looks right, click Export in the top bar. There are presets for YouTube, TikTok / Reels, X / Twitter and a Draft preview, which renders at half resolution for a quick check. Pick MP4, WEBM or GIF at 24, 30 or 60 fps. A short speed-ramp loop works well as a GIF.

Changing speed on your phone or desktop

The same editor runs as apps for iPhone (iOS 16.4 or later), Android (7.0 or later), Mac (Apple Silicon) and Windows, all at vidmoat.com/download. Sign in with the same account and your cloud projects follow you. @vidmoat_bot on Telegram uses the same projects and credits, so you can send a clip and ask for the speed change in plain words.

What the free plan gives you

You can start on the free Hobby plan with no card. Hobby exports are capped at 720p on the short edge, so vertical video comes out at 720x1280, and they carry a small Vidmoat watermark and a two-second end card. Creator at $19 a month removes the watermark and unlocks 4K, which you set in Project Settings before you export, because the export mirrors the project canvas.

I'll be straight about one thing: Vidmoat is young, and a small operation compared with the bigger players. If you need slow motion that invents extra frames, it doesn't do that. For speed changes, ramps and reverse on a real timeline, it does the job.

Common mistakes when changing video speed

• Slowing down low-frame-rate footage too far. Frames get repeated, so the motion steps. Shoot at a higher frame rate if you plan slow motion.
• Changing the whole clip when you meant a section. Split first, so only the part you want is affected.
• Ramping with no reason. One ramp on the moment that matters beats a ramp on every cut.
• Confusing J/K/L with clip speed. Those keys are for previewing.
• Leaving gaps after a speed change. Check the neighbouring clips and keep Snap on.

FAQ

Can I speed up a video online for free?
Yes. You can work on the free Hobby plan with no card. Exports carry a small watermark and a two-second end card, and are capped at 720p on the short edge.

How slow or fast can I make a clip?
Playback Speed goes from 0.05x to 10x.

Can I slow down just one part of a video?
Yes. Split the clip with B around the section, then change the speed of that section, or use speed keyframes inside a single clip to ramp in and out.

Will slow motion look smooth?
It depends on the footage. Vidmoat repeats source frames when slowing down and doesn't generate new ones, so footage shot at a higher frame rate looks smoother.

Does changing speed use AI credits?
Not if you do it by hand. Manual editing never costs credits; agent runs do.

Try it free

Upload a clip, set its speed, ramp into the moment that matters, and export, or ask the agent to time-remap it for you. Try it free at vidmoat.com/auth/signup.

Fred Abila builds Vidmoat.