Video Merger turns several clips into one video, even a mix of portrait and landscape footage, MP4 and MOV files, and clips with or without sound. All of the work happens inside your browser tab: your footage is never uploaded, and the download carries no watermark.
How to merge videos
- Click "Choose videos" or drop files on "Drop video clips here"; later batches join the end of the strip.
- Drag a card by its thumbnail into play order, or use "Move left" and "Move right". Then use "Trim", "Mute" or "Remove" on any card - the "Trim" view also has "Rotate" for a sideways clip.
- Pick "No transition", "Crossfade" or "Fade through black" in each gap between cards, or choose one under "Every gap" and press "Apply to all".
- Set "Frame shape", "Fit", "Format", "Quality" and "Transition length", and click "Add music" if you want a soundtrack under the merged video.
- Press "Merge videos", keep the tab open until the progress bar finishes, then click "Download merged video".
Merge Videos in Your Browser - Join Clips, Add Music and Transitions
freetoolonline.com editorial team
To merge videos, add two or more clips to Video Merger, drag them into order, trim or mute any of them, choose transitions, music and a frame shape, then press "Merge videos". You get a playable preview, a summary of clip count, duration, resolution, size and engine, and one MP4 or WebM file to download.
Clip cards, trims, rotation and previews
Every clip gets a card in play order with a thumbnail, file name, trimmed duration, resolution, a landscape, portrait or square hint and a bar that shows which part of the clip is kept. "Trim", or a tap on the thumbnail, opens the clip as a strip of frames with a start handle and an end handle that move in 0.1-second steps - drag them or use the arrow keys - and the card's duration updates as you drag. In the same view, "Rotate" turns the whole clip 90°, 180° or 270° clockwise; the preview, the strip of frames and the card thumbnail show it turned, and a merge with a rotated clip is re-encoded. "Preview" plays only the trimmed range; if the browser cannot play that codec, it says so, and the clip is still merged. Audio-only files are refused as clips with a message, though "Add music" accepts them.
Mixed clips in one frame shape
A merged video has one frame, so "Frame shape" sets it for the whole result. Original copies the first clip's shape, after any "Rotate" - drag the clip you want to match to the front. "Quality" sets the short side: 1080p or 720p, plus 4K on desktop browsers whose encoder reports it can encode 4K. Auto keeps the first clip's resolution with Original, never above 1080 on the short side; with a fixed shape it takes the largest clip's short side, capped at 1080.
| Frame shape | Size at 1080p | Size at 720p |
|---|---|---|
| 9:16 (vertical) | 1080 x 1920 | 720 x 1280 |
| 16:9 (landscape) | 1920 x 1080 | 1280 x 720 |
| 1:1 (square) | 1080 x 1080 | 720 x 720 |
| 4:5 (portrait) | 1080 x 1350 | 720 x 900 |
"Fit" handles clips whose shape differs from the frame. "Letterbox (show the whole clip)" scales a clip to fit inside and fills the empty area with black bars, so nothing is cut off. "Crop to fill" scales it until it covers the frame, keeps the center and trims the overflow at the edges - no bars, but a landscape clip in a 9:16 frame keeps only its middle. "Try two sample clips" loads one landscape and one portrait demo clip to compare both fits.
Transitions and background music
"Crossfade" overlaps two neighboring clips: the picture dissolves from one into the next while the two soundtracks crossfade, so each crossfaded gap makes the merged video shorter by the transition length. "Fade through black" fades the first clip's picture and sound to black and silence, then fades the next clip in, keeping the total length. The "Transition length" is shortened automatically when a clip is too short to hold it.
"Add music" lays an audio track - MP3, M4A/AAC, WAV, OGG, Opus, FLAC or another format the browser can decode - under the merged video, and the "Music volume" slider sets its level from 0 to 100% (80% by default). "Clip audio while music plays" controls the sound recorded with the clips:
- "Keep" leaves clip sound at 100%, mixed with the music.
- "Lower" turns clip sound down to 25% under the music - the default once a track is added.
- "Mute" drops clip sound to 0%, so the music becomes the only soundtrack.
Two checkboxes start switched on: "Loop music if it is shorter than the video" repeats a short track to the end, and "Fade music out at the end" fades it over the last 2 seconds. A clip with no audio track, or one muted on its card, contributes silence, which keeps picture and sound in sync.
Lossless join, browser encode or compatibility mode
Video Merger picks the method itself and shows it in a badge during the merge. Before you start, the output line already names the format, for example "Output: MP4 (H.264 + AAC)". "Format" lets you pick the file type instead of "Auto (best for this browser)": "MP4 (H.264)", "WebM (VP9)" or "WebM (AV1)"; a choice this browser cannot encode is greyed out, and compatibility mode always makes MP4 (H.264).
| Badge | Used when | Speed | Output |
|---|---|---|---|
| Lossless join - no re-encode | All clips share one encoding (codec, settings, resolution, rotation flag, audio) and no edit needs new pixels or sound | Usually seconds - the data is copied | .mp4 for H.264 or HEVC clips, .webm for VP8, VP9 or AV1 clips; no quality loss |
| Encoding in your browser (WebCodecs) | Everything else - mixed clips or any edit | In tests on a recent laptop, less than the video's running time; slower on older or low-power devices | MP4 (H.264 + AAC), or WebM (VP9, AV1 or VP8 + Opus) when the browser cannot encode H.264; up to 60 fps |
| Compatibility mode (slower) | No WebCodecs, a codec the browser cannot decode (such as HEVC in Chrome without a hardware decoder), AVI and other containers the main engine cannot read, or an encoder failure | Slower - it runs a single-thread WebAssembly copy of FFmpeg, and in some browsers a merge takes many times the video's length | MP4 (H.264 + AAC), at most 720p and 30 fps |
Check for yourself that nothing is uploaded
Open the browser's developer tools, switch to the Network tab and run a merge. The only requests the tool itself makes are for its own code files from freetoolonline.com: Mediabunny (about 0.7 MB), an AAC audio encoder (about 1 MB, only in browsers without a built-in one, such as Safari versions before 26) and FFmpeg.wasm (about 31 MB, only in compatibility mode). The browser caches each one after its first download, and your own files never appear in that list.
Merge, split, trim, edit or convert
Video Merger joins clips; it does not add text, captions or effects, or split one clip into pieces. Other video tools cover those jobs.
| What you want to do | Tool to use |
|---|---|
| Join several clips into one video | Video Merger |
| Cut one video into separate pieces | Video splitter |
| Keep a single range of one video | Video trimmer |
| Add titles, captions, effects or keyframes on a multi-track timeline | Video editor - "Edit in Video Editor" opens your clips there with their trims, rotations, mute and music |
| Change the format of one file | HD video converter (also runs in your browser) |
Frequently Asked Questions
Do I need an account, and does the download carry a watermark?
No to both. There is no account, sign-up or login, and the merged file - named like merged-3-clips.mp4, or .webm - downloads without a watermark. There is no cloud save or project file either; "Merge again" keeps your clips and settings for another run, so you can try a second version with a different frame shape or soundtrack.
Are my videos uploaded to a server?
No. The browser reads your clips and music straight from your device and builds the merged file in the tab's memory, so no clip, music track or finished video is sent anywhere. Pressing "Start over" or closing the tab releases the clips and the result, and nothing is stored once the tab is closed.
Can I merge clips with different formats, sizes or orientations?
Yes. "Choose videos" accepts MP4, MOV, M4V, WebM, MKV, AVI and other video types your browser lists, and one merge can mix them. Portrait phone clips are turned upright, and a clip that still plays sideways or upside down can be turned 90°, 180° or 270° clockwise with "Rotate" in the view that "Trim" opens. "Frame shape" and "Fit" set how each clip sits in the single output frame, and the output takes the highest clip frame rate, rounded to a standard rate within the engine's cap.
Will merging reduce the video quality?
Only if the clips are re-encoded. A trim, a mute, a rotation, a transition, music, a "Frame shape" other than Original or a "Quality" other than Auto forces a re-encode, even for clips that would otherwise get the "Lossless join - no re-encode" badge. Re-encoding uses a high quality setting but is not bit-identical, and HDR or 10-bit clips become standard 8-bit video, so their colors can look different.
Is there a file size limit?
Only your device's memory sets one; there is no server-side cap. Before merging, the tool warns when the estimated output passes about 1.5 GB with browser encoding, or when the clips add up to more than about 500 MB in compatibility mode on a desktop. Phones get that warning at lower sizes.
Can I merge videos on my phone?
Yes. It runs in Safari 16.4 or newer and in current Chrome, Edge and Firefox, though Firefox on Android has no WebCodecs and uses the slower compatibility mode. On a phone, keep the tab in the foreground until the merge finishes: some browsers pause background tabs, and closing the tab stops the merge. The tool asks the browser to keep the screen awake where supported.
Can I add background music and still hear people talking?
Yes. After you click "Add music", leave "Clip audio while music plays" on Lower or switch it to Keep, and pull the "Music volume" slider down if voices still get buried under the track. To silence one noisy clip without touching the others, press "Mute" on its card; there is no separate volume level for each clip.
Can I use a different transition between each pair of clips?
Yes - each gap between two cards has its own selector, so one cut can stay plain on "No transition" while the next uses "Crossfade" or "Fade through black". Only the timing is shared: a single "Transition length" of 0.5, 1 or 1.5 seconds covers every gap. Wipes, slides and other styles are not offered.
Why is my merge slow, or why did it stop with an error?
Speed depends on the device and browser. If the badge reads "Compatibility mode (slower)", single-thread FFmpeg.wasm is doing the work. A failed merge shows a red panel naming the clip and the reason - an unsupported codec, an unreadable file or not enough memory. Remove or replace that clip and try again. DRM-protected video cannot be merged.