Free Split Screen Video Maker

Worked example

Press "Try a sample". After a few seconds the page lists two 6-second clips: a landscape one named "sample-video.mp4" (or "sample-video.webm", depending on what your browser can record) and a portrait one named "sample-portrait.webm". The Layout buttons are "Side by side" and "Top and bottom". Under the preview the line reads "1280×720 · 0:06 · ~1.3 MB", because Shape starts on 16:9, Resolution on 720p, Length on "Shortest" and Quality on "Balanced". Click "Top and bottom": Shape switches to 9:16 and the line changes to "720×1280 · 0:06 · ~1.3 MB". Press "Make split screen video". The button counts "Making the video 40%… (tap to cancel)", then the page says "Your split screen video is ready." with a player and a download button. The file is named "sample-video_split_screen.mp4".

Which settings to use, and the limits

• Pick the layout that matches the number of clips. The tool takes 2 to 4 clips. With 2 the layouts are "Side by side" and "Top and bottom". With 3 they are "Three in a row", "Three stacked" and "One big, two small". With 4 they are "2 × 2 grid" and "Four in a row". The first clip takes the first cell: left or top, the big one in "One big, two small", and top left in the grid, which fills row by row. The arrow buttons ("Move earlier" and "Move later") change the order. If the current layout does not fit a new clip count, the tool switches to the first layout for that count.
• Set the layout first, then the shape. Each layout starts with a shape: 9:16 for "Top and bottom" and "Three stacked", 1:1 for "2 × 2 grid", and 16:9 for the rest. Choosing a layout resets Shape, so change Shape afterwards. Shape offers 16:9, 9:16, 1:1 and 4:5. Resolution sets the short side, "720p" or "1080p", so 16:9 is 1280×720 or 1920×1080, 9:16 is 720×1280 or 1080×1920, 1:1 is 720×720 or 1080×1080, and 4:5 is 720×900 or 1080×1350. "1080p" has 2.25 times the pixels of "720p", which means more to encode and a bigger file.
• Choose between "Fill (crop edges)" and "Fit (show all, add bars)". Under "Each clip", "Fill (crop edges)" scales a clip until it covers its cell and trims what spills over, so a 16:9 clip in a tall 9:16 cell loses its sides. "Fit (show all, add bars)" shrinks the clip until all of it shows and pads the rest with bars. The bars, the canvas and the gaps all use one colour: the "Colour" picker next to "Border", which starts on black. "Border" sets the gap between cells to "None", "4 px", "8 px" or "16 px", measured on the finished frame, not on the smaller preview.
• Set Sound and Length together. "All clips mixed" adds the sound of every clip that has any, each at its own loudness, with a limiter so loud clips do not distort. "Only clip 1" (or 2, 3, 4) keeps one clip's sound, and "No sound" makes a silent video. A clip with no audio track adds nothing. Under "Length", "Shortest" ends when the shortest clip ends, so longer clips are cut. "Longest" runs to the end of the longest clip, and the others hold their last frame. Sound is encoded as AAC at 160 kbps.
• Pick a Quality and read the size line. "High", "Balanced" and "Small file" encode H.264 at constant-quality values (CRF) of 20, 23 and 28; a lower number means better quality and a bigger file. The result is always an .mp4 at 30 frames per second, whatever the clips use. The line under the preview shows the size, the length and a rough file size marked with "~". For 30 seconds at 720p it is about 6.5 MB on "Balanced", 10.5 MB on "High" and 3.5 MB on "Small file". It is an estimate, not a promise.
• Know the limits before adding long clips. You can add up to 4 clips, and each is checked on its own. A clip above about 2 GB is refused on a normal computer, 1 GB on a computer reporting 4 GB of memory or less, and 400 MB on a phone, with a caution above 800 MB, 400 MB and 150 MB. Where the browser allows it, clips are read from disk instead of being copied into memory, but the finished video is built in memory before download. The engine, about 31 MB, starts loading when you add the first clip and is cached afterwards. Your clips are processed in the browser and are not uploaded.

Common problems and how to fix them

It says "Up to 4 videos fit in one split screen. The extra ones were left out."

You picked more clips than there is room for, or added a fifth after four were already in. The clips that fit are kept, in the order you picked them, and the rest are dropped. Remove one with the ✕ button ("Remove") and add the one you want instead, or press "Start over". To show more than four, make one split screen first and add the result as a clip in a second one.

It says "This file is 2.6 GB, which is too large to process in your browser on this device (limit ~2 GB). Try a smaller file or trim a shorter clip first."

The size check runs on each clip as you add it, against a limit that depends on the device: about 2 GB, 1 GB or 400 MB, as listed above. The message gives the size but not the file name, so compare it with your clips' sizes. Other clips picked at the same time are still added. Cut the clip shorter in the Video Trimmer, or use a computer. A clip above the lower caution size is accepted with an amber warning, but can still run out of memory.

It says "Could not read how long these videos are. Try saving them as MP4 first."

Before encoding, the tool needs each clip's length. It takes it from the browser, and for a clip the browser cannot read (some AVI and MKV files) it asks the engine. This message appears only when none of the clips has a readable length. If only one length is unknown, the tool carries on and ignores that clip when it works out the result length. Save the clips as MP4 (H.264) and add them again.

It says "Something went wrong while processing this file. Try a different output format or a different source file."

This is the general failure message, for when the engine stops without saying why. An AV1 clip, a damaged file, an unusual codec and running out of memory each have their own message instead, but none of them says which clip caused it. There is no output format to change in this tool. Remove the clips one at a time to find the bad one, then save that clip as an MP4 (H.264) and add it again.

The finished video has no sound.

Sound only comes from clips that have an audio track. The result is silent if Sound is "No sound", or if it is "Only clip 3" and that clip has no audio, and the tool does not warn you. With "All clips mixed", clips without audio are skipped, so the result is silent only when none of them has sound. Play each clip on its own to check, then choose a clip that has sound or "All clips mixed".

How it compares

This tool plays 2 to 4 clips at the same time in a fixed layout and saves one MP4. To play clips one after another, use the Video Merger instead. Every clip starts at 0:00. There is no trimming, no time offset between clips and no zoom or position control inside a cell, so a reaction video that needs both sides lined up has to be cut beforehand, for example in the Video Trimmer. The picture is always re-encoded as H.264 at 30 frames per second, and you choose from seven layouts rather than drawing your own. A desktop editor can line clips up and take files above the browser limits. In exchange, nothing is installed and the clips stay in your browser.