Adapt a video to a new aspect ratio
Turn 16:9 into 9:16 or 1:1: the picture is fitted to the new frame the way you choose, and the subtitles are reflowed into the safe area of the new frame, with line length rewrapped to the new width. Everything runs in the browser — the video is not uploaded.
The video is never uploaded — everything runs in your browser.
The video is never uploaded — everything runs locally in your browser
Need more aspect ratios × more languages?
The full version takes the video, produces bilingual subtitles in several languages at once, and burns them into a ready-to-publish file in the same place.
Sign up free and get trial creditsFAQ
Why do subtitles so often go wrong when you go from landscape to portrait?
Because “cropping the picture” and “positioning the subtitles” are two separate calculations. When an ordinary tool center-crops 16:9 to 9:16, subtitles that sat at the bottom get cropped out of the frame, or land in the middle of the new frame and cover the face. A subtler case is that the subtitles are still in the frame but end up under the platform UI — the bottom of a portrait screen holds the progress bar, the account name and the action buttons, taking up about 14% of the height. This tool calculates the two together: the picture is fitted to the new frame, the subtitles are re-laid-out against the new frame’s safe area and line length, and the shift is reported to you explicitly.
How do I choose between the three fill modes?
For a talking-head or product video with the subject centered, pick “Center crop”: the frame is filled and cleanest, at the cost of losing both sides. To keep the whole frame’s information (charts, slides, the full product), pick “Blurred background”: the original picture stays fully visible and is topped and tailed with a Gaussian blur of itself. For screen recordings and serious content, pick “Black bars”: the least likely to pull focus. When the aspect ratio changes a lot, crop can also be set to “Top” to keep faces in view.
Why do the subtitles look bigger in portrait?
Font size is defined as a percentage of the picture height, so when the aspect ratio changes the percentage stays the same and the pixel size stays the same too. But the frame is narrower, so the same font size takes up a more conspicuous share of the picture — which is exactly what short-form video wants. Be aware of the cost that comes with it: a 9:16 frame is 1080 wide, 44% narrower than the 1920 of 16:9, so a sentence that fit on one line will overflow, and here it wraps at punctuation rather than cutting mid-character.
Why is loudness normalization off by default?
Loudness normalization (EBU R128) requires re-encoding the audio, and re-encoding is lossy. If all you want is to turn landscape into portrait, having it on by default would cost you a step of audio quality for nothing, so we made it a manual switch — turn it on when you need loudness matched to a platform’s delivery spec. Same for speed changes: at 1× the audio is not processed and the original track is used.
What happens if my computer can’t keep up?
Transcoding runs on your own CPU, and a 3-minute video usually takes several minutes in the browser. The page shows progress in stages (reading → transcoding → burning → muxing) and you can cancel at any point; after you pick a video it also gives a time estimate up front. On a low-spec machine with a long video it may genuinely not finish, so we kept a zero-cost way out: click “Export reflowed subtitles only” — no transcoding engine is loaded and no video is transcoded, and you get an ASS subtitle file with positions and line breaks already adjusted for the new frame, ready to burn with another tool.