Use the tool
Privacy-conscious: this tool runs in your browser where practical, so your working input stays on your device unless the page explicitly says otherwise.
Output format is selected automatically from formats supported by your browser.
Keep this tab open. Browser video encoding runs in real time and can take approximately the video duration.
ToolsDiary handles dimensions and framing. If you also need trimming, captions, transitions, effects or final creative editing, CapCut is an optional third-party editor you can continue with.
Video Compression vs Resizing: How to Prepare Videos for Social Media
Learn the difference between compressing a video and resizing its dimensions, when to downscale or crop, and how to prepare practical versions for social media and web uploads.
What this tool does
Use this social media video resizer to change video dimensions and aspect ratio for vertical, portrait, square or custom layouts. Choose presets for Instagram Reels, YouTube Shorts, TikTok, Facebook and other common social workflows, then decide whether to fit the full source frame or fill the target canvas with a centered crop. Preview the framing before export and create the resized copy locally in your browser without uploading the source video to ToolsDiary.
Resizing a social video is mainly a framing problem, not just a file-size problem. A landscape source placed inside a vertical 9:16 canvas can either remain fully visible with background space or be enlarged and cropped to fill the screen. Neither option is universally better: the right choice depends on where faces, captions, products and other important details sit in the original frame. Platform requirements can change, so ToolsDiary presets are practical starting dimensions and should be checked against the current publishing destination when a campaign has strict specifications.
Useful for
- Resize landscape or square footage into a vertical canvas for Reels, TikTok and YouTube Shorts workflows.
- Create 4:5 portrait and 1:1 square versions for social feed placements.
- Prepare several aspect-ratio versions from one source clip without installing a desktop editor.
- Use Fit when the complete source frame must remain visible, or Fill / crop when edge-to-edge coverage matters more.
- Create a custom video width and height when an ad platform, publisher or CMS specifies exact dimensions.
How to use it
- Choose a supported video and wait for the source dimensions and duration to appear.
- Select a platform preset or choose Custom and enter the target width and height.
- Choose Fit to preserve the entire source frame with background space, or Fill / crop to cover the target canvas edge to edge.
- Check the preview carefully for faces, captions, logos and products near the edges of the crop.
- Choose output quality, start the local resize, then preview and download the finished copy if the framing looks correct.
Worked examples
Landscape clip for vertical short-form video
Input16:9 landscape source · 9:16 target · Fit
ResultThe full landscape frame remains visible inside a vertical canvas with background space around it.
This avoids cropping but does not create an edge-to-edge vertical composition.
Landscape clip filling a 9:16 canvas
Input16:9 source · 9:16 target · Fill / crop
ResultThe video fills the vertical canvas while portions of the left and right sides are cropped.
Check that faces, products and text are not positioned in the cropped areas.
Feed portrait version
InputWide source · 4:5 target
ResultA taller portrait-oriented version suitable as a starting point for feed placements that use 4:5.
Confirm the destination platform’s current requirements before a paid campaign or strict upload.
Square social version
InputVertical or landscape source · 1:1 target
ResultA square canvas that can either preserve the whole source with padding or crop it to fill.
Square output can be useful when one asset needs a balanced feed-friendly layout.
Common mistakes to avoid
- Choosing Fill / crop without checking whether faces, captions or logos fall outside the new frame.
- Assuming every social platform uses one permanent video size for all placements.
- Stretching footage to a new aspect ratio and unintentionally distorting people or products.
- Using Fit but forgetting that the added background becomes part of the final composition.
- Resizing an already low-resolution source upward and expecting genuine new detail.
Before you use the result
- Confirm the final width, height and aspect ratio match the intended publishing placement.
- Watch the preview for cropped faces, captions, logos, product details and UI elements.
- Check that the subject is not stretched or unnaturally distorted.
- Play the exported file to verify motion, audio and framing before publishing.
- Keep the original so you can create another aspect-ratio version without re-encoding an already resized copy.
Edge cases and limitations
- A centered crop may not work when the important subject stays near one edge of the original frame.
- Burned-in captions close to the edges can be cut off when converting landscape footage to vertical.
- Browser encoding support varies, so output format may differ between devices.
- Very long or high-resolution footage can require substantial processing time and memory in the browser.
- Exact ad-placement specifications can differ from general organic social presets and can change over time.
Practical tips
- Use 9:16 when you specifically need a full-screen vertical canvas, but verify the current destination requirements before publishing.
- Use Fit when preserving every part of the source frame is more important than filling the canvas.
- Use Fill / crop when edge-to-edge coverage matters, then check the crop before export.
- Keep important captions, faces and logos away from extreme edges when you know one source will be adapted into several aspect ratios.
- If the finished file also needs to be smaller, resize for framing first and then use the Video Compressor as a separate final optimization step.
Frequently asked questions
How do I resize a video for Instagram Reels, TikTok or YouTube Shorts?
Choose your source video, select the relevant vertical preset or 9:16 target, decide between Fit and Fill / crop, preview the framing and export the resized copy. Check the destination platform’s current requirements before publishing.
What aspect ratio is used for vertical short-form video?
9:16 is a common full-screen vertical format used by major short-form platforms. Individual placements and publishing rules can change, so confirm current requirements when exact compliance matters.
What is the difference between Fit and Fill / crop?
Fit keeps the complete source frame visible and may add background space. Fill / crop enlarges the source until the target canvas is covered, which can remove content from the edges.
Are my videos uploaded to ToolsDiary?
No. Supported videos are read, previewed and re-encoded locally in your browser rather than uploaded to ToolsDiary.
Can I resize a landscape video to vertical?
Yes. You can place the landscape frame inside a vertical canvas with Fit or crop the sides with Fill / crop. The best choice depends on where the important subject appears.
Will resizing a video reduce its file size?
It can, especially when the new dimensions are smaller, but file size also depends on duration, codec and encoding quality. Use the Video Compressor when reducing file size is the primary goal.
Does resizing change video quality?
Re-encoding can introduce some quality loss, and upscaling cannot create real detail that was not in the source. Preview the exported result before publishing.
Can I enter a custom video size?
Yes. Use the Custom option when you need an exact width and height instead of one of the included social presets.