Edit a recording on the web

The video editor turns a recording in your Library into a finished video: trim and cut it, crop it, add captions, text, arrows, pictures, other videos, a voice-over and music. Every change is kept as a list of edits next to the recording. The recording itself is never changed, and the edits play for everyone who opens your link.

The video editor is part of the Web app plan. See Plans and billing.

Open the editor#

1. Open your Library at catu.app/library and click a recording.
2. Click “Edit video” at the top of the page.

The editor fills the window: a bar along the top, the tools down the left, the player in the middle, a panel that opens on the right, and the timeline underneath.

“Edit video” is there only for your own recordings. For a screenshot, the button is “Mark up” instead.

On a phone, “Edit video” sits in the ⋯ menu and shows “Not optimised for mobile”: video editing on the web is made for a computer or an iPad. If the window becomes phone-sized while you edit, the same notice appears, and the editor closes when you dismiss it.

The top bar#

From left to right:

• The title. Click it to rename the recording. Press Return to save the new title, or Esc to put the old one back.
• The time. The playhead's time and the recording's length, then plays and how long the edited video runs, for example “0:12 / 1:30 · plays 1:04”. unsaved is added while you have changes that are not saved.
• “Clear trim” appears once you have trimmed the start or the end. It plays the whole recording again. Your cuts stay.
• Undo and Redo (the curved arrows). They go back and forward through your changes, up to 100 steps.
• Discard (the bin). Throws away everything since the last save.
• “Save”. Saves your edits. See Save, discard and exit.
• Exit (×). Closes the editor.

The tools on the left#

Each tool opens its panel on the right. Click the tool again to close it.

Tool	What it adds
AI	Any edit, asked for in words. See Ask the AI.
Captions	Lines of speech at the bottom or top of the picture.
Video	Another video over the recording, before it or after it: an intro, an outro, a logo, a stock video, a GIF or picture-in-picture.
Audio	A voice-over you record or type, music, sound effects or an audio file.
Text	A line of text on the picture.
Image	A picture: one of yours, a file, a photo from Pexels or one made with AI.
Items	Arrows, highlights, shapes, checkboxes, hearts, tooltips, buttons, emoji and stickers.
Effects	Blur, zoom, loupe and dim.

The Text, Items and Effects panels list what is already on the timeline, with an add button on top. Click a row in the list to open its settings, or the bin to remove it.

Everything you add starts at the playhead and lasts 3 seconds, unless it has its own length (a video or a sound).

Move, resize and time what you add#

On the picture:

• Drag an item to move it. Click an empty part of the picture to deselect it.
• Drag a corner of the selected item to resize it. Pictures, videos, shapes and the loupe keep their shape; hold ⇧ while you drag to stretch them.
• Drag the round handle at the tip of an arrow to aim it.
• A tooltip sizes itself to its text, so it only moves.

An item may hang off the edge of the picture. Four light corners around the picture mark what plays and what is downloaded.

In time, each item has a bar on the timeline: drag the bar to move it, or drag its ends to make it shorter or longer. Its panel also shows Start and End. Click a time to type one, for example 1:02.5, then press Return. The pin button next to a time sets it to the playhead.

Trim and cut#

To trim the start or the end: on the Video row of the timeline, drag the handle at the left or right end. The trimmed part is shaded and does not play. “Clear trim” in the top bar undoes both.

To cut a part out of the middle:

1. Move the playhead to where the part starts.
2. Click “Cut” above the timeline. A red marker stays at that point.
3. Move the playhead to where the part ends. You can also drag the red marker, or type either time.
4. Click “Cut this out”.

“Cancel” (or Esc) stops without cutting.

Cut parts are hidden on the timeline: a seam shows where each one was. Click the ✕ on a seam to put that part back. “Show cuts” shows them in place, hatched; “Hide cuts” hides them again.

Crop the picture#

1. Click “Crop” above the timeline. A frame appears over the picture.
2. Drag inside the frame to move it, or drag an edge or a corner to resize it. Its size in pixels shows in the corner.
3. Click “Done”.

While cropping, the bar above the timeline also has:

• a list of shapes: “Free”, “9:16 Vertical · Reels, TikTok, Shorts”, “4:5 Portrait · Instagram”, “1:1 Square”, “16:9 Wide · YouTube”, “16:10”, “4:3”, “3:2”, “2:1” and “21:9 Cinema”;
• the width and height in pixels, which you can type;
• “Center”, which centres the frame on the picture;
• “Full”, which removes the crop.

The recording's size, position and sound#

The recording itself can be treated as a layer. Click the Video row on the timeline to open the Recording panel:

• Size: from 10% to 100% of the picture. You can also drag the recording on the picture to move it, or drag its corners to resize it. Hold ⇧ to stretch it.
• “Reset to full picture” puts it back.
• Transparency: how solid the recording is, from 0% to 100% solid. “Reset to solid” puts it back.
• Volume, “Mute” and “Reset to 100%” for the recording's own sound.

Click the Audio row under it for the volume alone, with a list of the audio you added.

A smaller or see-through recording is how a video placed behind it shows through. See Layers.

Captions#

Captions are one line at a time, light text on a soft dark backing, at the bottom centre. Lines never overlap.

Make captions#

Click Captions on the left, then “Add captions”:

• “Add a line at the playhead” adds an empty line where the playhead is. Type its words straight away.
• “Lines from the recording” uses the speech your Mac wrote down while you recorded. “Rebuild from the recording” replaces the lines you have with fresh ones.
• “Generate from the video” appears when your Mac left no transcript, for example for a video uploaded on the web. The sound goes to OpenAI through catu once; the transcript comes back and is kept with the recording, encrypted, so it never needs making again. See Notes your Mac makes.
• “Upload SRT / WebVTT” reads a subtitle file, up to 2 MB. It replaces any lines already there; with lines on the video, the item is called “Replace with a file…”.
• “Download as .srt” and “Download as .vtt” save the lines as a subtitle file, for example to upload to YouTube.

The switch at the top of the panel shows or hides all the captions on the video. Hidden lines come back with the switch until you save.

Edit the lines#

The panel lists every line with its start time.

• Click in a line to change its words. Return finishes.
• Click a line's time to type when it starts and ends (From and To), then click “Done”.
• The bin next to a line removes it.
• Click a line's bar on the timeline to open its own panel, with Position: “Bottom” or “Top”. The arrow at the top goes back to all captions.

How captions look#

With captions on the video, the panel has settings for every line at once:

• Size, in seven steps from XX-small to XX-large. The arrows make it smaller or larger.
• Text colour.
• Background (click to unfold): its Colour, its Transparency and Blur behind, which blurs the picture behind the backing by up to 30 px.

“Reset the look” puts back the usual look.

Voice-over from the captions#

Choose “Voice-over from the captions” in “Add captions”, pick a voice and click “Make the voice-over”. Each line becomes a spoken take in that voice, joined to its line: move the line and its take moves too. The takes are listed under their lines.

Text#

Click Text, then “Add text”. Its panel has:

• Text: the words, up to 200 characters.
• Font: any Google Font. Type in “Search Google Fonts…” to find one.
• Size: seven steps from XX-small to XX-large.
• Align: left, centre or right.
• Text colour.
• Background: on or off, with its Colour and Transparency.
• Shadow: on or off, with Shadow strength.

With two or more texts, “Sync all text styles” in the Text list gives every text the font, size, alignment, colours and shadow of the one you opened last.

Tooltips and buttons#

Both are in Items › “Add an item”: “Tooltip” and “Button”.

A tooltip is a speech bubble that points at something. Its panel has Text, Font, Size, Pointer (which side the point is on: top, bottom, left or right), Text colour, Background colour and Shadow.

A button looks like a button on the video. Give it a Link and people who watch can click it to open that address in a new tab. Its panel has:

• Text and Link (a web address; https:// is added if you leave it out);
• Font, Text size and Text colour;
• Background: on or off, with its colour and Transparency;
• Outline: on or off, with Outline weight from 1 to 12 px;
• Shadow and Shadow strength;
• Corners: “Square”, “Soft”, “Round” or “Pill”, when the button has a background or an outline.

Arrows, highlights and shapes#

Click Items, then “Add an item”, and choose “Arrow”, “Rectangle” (a highlight frame), “Circle”, “Oval”, “Square”, “Checkbox” (a ticked box) or “Heart”.

Their panel has Line weight, in seven steps from XX-small to XX-large, and Colour. The checkbox and the heart are filled, so they have no line weight.

The same menu adds pictures that belong with these marks:

• “Emoji” opens a grid you can search. The emoji is added as a picture.
• “Sticker library” searches animated stickers from GIPHY.
• “Create with AI” makes a sticker from your words: a cut-out on a see-through background, made by OpenAI through catu. It takes up to a minute.

Emoji and stickers have the same settings as pictures.

Effects: blur, zoom, loupe and dim#

Click Effects, then “Add an effect”:

Effect	What it does	Setting
Blur	Blurs the area inside its box, for passwords, emails or names.	Blur: 2 to 60 px.
Zoom	The whole picture zooms in on its box while it lasts, then back out.	Its box: drag and resize it on the picture.
Loupe	A round magnifier over one spot.	Magnify: 1.5× to 4×.
Dim	Darkens everything except its box.	Keep clear: “Box” or “Oval”. Darkness: 30% to 95%.

Blur covers the box for the whole time its bar lasts. If what you are hiding moves or stays on screen longer, make the box bigger or the bar longer.

Pictures#

Click Image, then “Add image”:

• “Choose from your media” shows pictures you have added to any of your videos, ready to use again.
• “Create an image with AI”: describe it, choose the Shape (“Wide”, “Square” or “Tall”) and whether it has a See-through background, then click “Create”. It is made by OpenAI through catu and takes up to a minute.
• “Find a photo on Pexels” searches free photos.
• “Upload a file”: PNG, JPEG, WebP, GIF or SVG, up to 10 MB.

The picture is added in the middle, at the playhead. Its panel has Rotation, Opacity and Rounded corners.

Moving GIFs from GIPHY are under Video, below.

Videos#

Click Video, then “Add video”:

• “Choose from your media”: videos you have added to any of your recordings.
• “Select from your videos”: your other recordings and uploads in the Library, up to 200 MB each. A copy is added to this one.
• “Find a stock video” searches free videos from Pexels.
• “Find a GIF” searches GIPHY.
• “Upload a file”: MP4, MOV or WebM, up to 200 MB.

The video is added over the whole picture, at the playhead, for as long as it lasts or until the recording ends. Its panel has:

• Place: “Before” plays it before the recording starts (the recording starts that much later), “Over” plays it over the recording at the playhead, “After” plays it once the recording ends.
• Start from: where it starts on the timeline.
• This video's volume, and Lower main recording volume (see ducking).
• Size: shrink it for picture-in-picture, then drag it into place.
• “Fill” or “Fit inside”: whether it fills its box or shows whole inside it. “Reset to full frame” makes it fill the picture again.
• Rotation, Opacity and Rounded corners.

On the timeline, drag the left end of its bar to skip the start of the video, or the right end to stop it sooner. A bar can't run past the end of its video.

Audio#

Click Audio, then “Add voice-over or sound”. Everything you add starts at the playhead.

Record a voice-over#

1. Choose “Record”.
2. Pick a Microphone, or leave “System default”.
3. Click the microphone button and allow the microphone if the browser asks.
4. After a 3-2-1 count, talk. The video plays without sound from the playhead so you can follow it.
5. Click “Stop”, or let the video reach its end.

The take is added where you started. “Cancel” throws it away.

Text to voice#

1. Choose “Text to voice”.
2. Under Voice, click the chosen voice to see the others. The play button lets you hear each one. The language menu (“Any language”) narrows the list.
3. Type what the voice should say, up to 1,500 characters.
4. Click “Add”.

The voices come from ElevenLabs through catu; your text is not kept. catu remembers the voice and language you choose, and the AI uses the same voice.

Music and sound effects#

• “Find music in the library” and “Find a sound effect in the library” search catu's own library, cleared for any video. Click the play button to hear one, and + or its name to add it.
• “Create music with AI”: describe the mood, style and instruments (not an artist or a song), pick a Length of 15, 30 or 60 seconds or “Full length”, and click “Make the music”. It is instrumental, up to 3 minutes, made by ElevenLabs through catu.
• “Create a sound effect with AI”: a few words, a length of 1, 2 or 5 seconds, then “Make the sound”.

Music is added at 25% volume, so it sits quietly under speech. Music and sound effects leave the recording's own sound as it is.

Upload a file#

Choose “Upload a file”, then “Choose a file…”: MP3, M4A, WAV or OGG, up to 50 MB.

Volume, speed and ducking#

Click any audio bar, or its row in the Audio panel, to open its settings:

• Its name at the top. Type to rename it.
• Start from: where it starts.
• Volume.
• Playback speed: 0.5× to 2×. The bar grows or shrinks to match.
• Lower main recording volume (ducking): while it plays, the recording's own sound drops to a fifth of its volume, then comes back. It is on for recorded takes, text to voice and uploaded files, and off for music and sound effects.

Drag either end of an audio bar to skip the start or stop it sooner.

Layers: what is in front#

Every item has its own row on the timeline. The order of the rows is the order on the picture: rows above the Video row play in front of the recording, rows below its Audio row play behind it. New items start in front; captions start in front of everything.

To change the order, drag a row up or down by its grip (⋮⋮) at the left.

Something behind the recording only shows where the recording does not cover it: make the recording smaller or less solid in the Recording panel.

The timeline#

• Move the playhead: click or drag on the ruler or on any row, or drag the playhead's knob.
• Zoom: the − and + buttons on the right, ⌘-scroll or Ctrl-scroll, or pinch on a trackpad. “Fit” shows the whole video again.
• The Video row shows pictures from the recording, the trim handles and the cuts. The Audio row under it shows the recording's sound.
• Before and after: drag a bar before the start or past the end of the recording to show it there. The timeline grows a before or after zone, where the picture is black apart from your items. Captions stay within the recording.
• Right-click a bar for “Duplicate”, “Split at the playhead” and “Remove”. Audio bars can't be split.
• Click a selected bar again to deselect it.

Select several bars#

• ⌘-click (Ctrl-click) bars to add them to the selection, or take them out.
• ⇧-click a caption to select every caption between it and the one already selected. Their panel then sets the Position of all of them.
• Drag any selected bar to move them all. Delete removes them all.

Keyboard shortcuts#

These work when you are not typing in a field. On Windows and Linux, use Ctrl for ⌘.

Key	What it does
Space	Play or pause
⌘Z, ⇧⌘Z	Undo, redo
← and →	One frame back or forward
⇧← and ⇧→	One second back or forward
Delete or Backspace	Remove the selected item, or every selected bar
Esc	Deselect, or stop marking a cut
Home and End	Go to the start or the end, when the timeline has focus (click it first)
⌘-scroll	Zoom the timeline
⇧ while resizing	Stretch a picture, video, shape, loupe or the recording

Ask the AI#

The AI button at the top of the tools lets you ask for any of this in words: cut the first ten seconds, blur the email field, add captions. It proposes the edits, the preview plays them, and you keep them or undo them. See Edit a recording with AI.

Save, discard and exit#

“Save” keeps your edits. The edit list is stored with the recording, encrypted with its key, and catu shows “Edits saved. They play for everyone who opens the link.” The recording itself is never changed, so you can open the editor again and change or remove any edit.

When you save, pictures, videos and sounds you added but no longer use are deleted, so they stop counting against your storage.

Discard (the bin in the top bar) goes back to the last save at once, without asking. Files you added since the last save are deleted, and the undo history is cleared, so this can't be undone.

Exit (×) closes the editor. It does not save and does not ask: save first, or your changes are lost when you reload or leave the page.

Download the video#

1. Exit the editor.
2. Click the download button at the top of the recording's page.
3. Pick a preset, or set each choice yourself:
   • Presets: “YouTube” (full size, high quality, with sound), “Website background” (720p, a small file, no sound), “Social” (1080p at 30 fps, with sound) and “GIF” (480p at 12 fps).
   • Format: “MP4” (H.264, plays everywhere), “MP4 HEVC” (smaller, for Apple devices; offered when your browser can make it), “WebM” (VP9, for the web), “GIF” (no sound, for chat and documents) or “Audio only” (AAC in an M4A).
   • Size: “Original” (or “Cropped” with its height, after a crop), then “1440p”, “1080p”, “720p” and “480p”, as far as they are smaller than the recording. GIFs go up to 720p.
   • Quality: “Best”, “High”, “Good” or “Small file”.
   • Frame rate: the recording's own, or 60, 30 or 24 fps; 15, 12 or 10 for a GIF.
   • Sound: on or off. The line under the choices says the size of the picture and about how big the file will be.
4. Click “Download”.

The file is made in your browser, with all your edits, captions and sound. Longer videos take a minute. Making video needs Chrome, Edge or Safari 17 or later. “Original file” downloads the recording as it was uploaded, without the edits.

A recording without edits at its own size and best quality downloads straight away as it was recorded; any other choice converts it first.

What viewers see#

Once you save, everyone who opens your link sees and hears the edited video: the trim, cuts and crop, captions, items, pictures, videos and audio. A button with a link opens it in a new tab when they click it.

If you allow downloads (see Passwords, expiry and downloads), their “Download” button offers the same choices: the edited video in the format and size they need, made in their browser, or the original file.

If something doesn't work#

• There is no “Edit video” button. It appears only on recordings you shared yourself. On a phone it is in the ⋯ menu and shows “Not optimised for mobile”. Edit on a computer or an iPad.
• Your changes are gone. Exit and Discard don't save. Click “Save” before you leave the editor.
• “The edits changed on another device”. The edits were saved somewhere else since you opened them. “Reload” loads those edits instead of yours. “Save anyway” replaces them with yours.
• “… isn’t connected yet.” The search for GIFs, photos, stock videos or sounds is not available at the moment. Upload a file instead.
• “That GIF has no video version; pick another.” Choose a different GIF.
• “The microphone was not allowed.” Allow the microphone for catu.app in your browser's site settings, then try “Record” again.
• “No room for a line there — move the playhead to a gap.” Caption lines can't overlap. Move the playhead to a moment with no line, or shorten the line next to it.
• A file is refused. Pictures can be PNG, JPEG, WebP, GIF or SVG up to 10 MB; videos MP4, MOV or WebM up to 200 MB; audio up to 50 MB; caption files SRT or WebVTT up to 2 MB.
• “This browser can't render video.” Download in Chrome, Edge or Safari 17 or later, or take the “Original file”.