How to Resize a Video for Instagram, TikTok and Reels

Short-form video platforms were all designed around a phone held vertically, which is why Reels, TikTok and similar formats expect 9:16 vertical video rather than the horizontal 16:9 shape most cameras and screen recordings default to. Preparing an existing clip for one of these platforms is usually a two-part job: getting the shape and length right, and getting the file size under whatever limit that specific platform enforces.

This guide covers the dimensions these platforms expect and the practical steps to get a clip ready.

The dimensions short-form platforms expect

Instagram Reels and TikTok are both built around a 9:16 vertical aspect ratio, most commonly 1080×1920 pixels — noticeably taller than it is wide, matching how a phone is held to record and to watch. A landscape (16:9) video played on these platforms typically appears letterboxed with black bars on the sides, unless it is specifically cropped or reframed to fill the vertical space.

Length and file size limits

Both platforms cap how long a clip can be and how large the uploaded file can be, and both limits have changed over time as the platforms have evolved — Reels and TikTok have both extended their maximum clip lengths more than once. Rather than relying on a specific number that may be outdated, it is worth checking each platform's current upload limits directly before a specific post, and treating "keep it well under the limit" as the safer default.

Getting an existing clip ready: trim first, then compress

A video that is too long for a platform needs trimming down to length first — cutting to the highlight or the section you actually want to post. Separately, if the resulting clip is still too large a file, compressing it reduces resolution and bitrate together to bring the size down without needing to cut any more content. These are two different problems solved by two different tools: trimming controls length and content, compression controls file size.

Step-by-step guide

Quick answer

What aspect ratio do Reels and TikTok expect? Vertical 9:16, most commonly 1080×1920 pixels — landscape video usually appears letterboxed unless it is reframed to fill that vertical space. In short, the Video Compressor lets you handle video compressor for free, directly in your browser, with your files staying private on your own device the entire time.

Common use cases

People turn to video compressor for all sorts of everyday reasons. If any of these sound familiar, the Video Compressor is built for exactly your situation:

• Handling a file quickly without installing software or creating an account.
• Encoding or generating exactly the output a website or workflow expects.
• Replacing a paid or upload-based tool with a free, private alternative.
• Producing something scannable, shareable or embeddable in one step.
• Keeping sensitive data on your own device instead of a remote server.

Whatever brought you here, the process is the same — quick, free and handled entirely on your own device — so you can get the result you need and move on.

Free ConvertProKit tools for this workflow

Everything in this guide is powered by free tools that run entirely in your browser — nothing is uploaded, there is no signup, and there are no watermarks or limits. These are the ConvertProKit tools that work best alongside the Video Compressor for video compressor:

• Video Compressor — get the job done free in your browser.
• Video Trimmer — get the job done free in your browser.
• Video to GIF Converter — get the job done free in your browser.
• Video Tools — get the job done free in your browser.

Because each one processes files on your own device, you can chain them together — for example convert, then resize, then compress — without a single file ever leaving your computer. That combination of speed and privacy is the whole point of a browser-based toolkit: there is no upload to wait for, no queue, and no server holding a copy of your data afterward.

All of these tools are part of the wider ConvertProKit collection of free online utilities, so once you are set up for video compressor you have dozens of related image, PDF, text and productivity tools a click away — every one of them free, private and instant, with nothing to install and no account to create.

Tips to get the best results

A few habits make video compressor smoother and keep your results consistently high quality. Keep these in mind whenever you use the Video Compressor:

• Confirm the tool processes files in your browser rather than uploading them, especially for anything private.
• Pick the output format based on where the file is going — compatibility and size often pull in different directions.
• Test the converted file in its destination before relying on it, so you catch any surprises early.
• Keep the original file until you have confirmed the conversion is exactly what you needed.

None of these take extra effort once they become routine, and together they are the difference between a result that is merely acceptable and one that is genuinely polished.

Common mistakes to avoid

Most problems with video compressor come down to a handful of avoidable slip-ups. Steer clear of these and you will get a clean result the first time:

• Assuming every online converter keeps your file private — many upload it to a server.
• Picking an output format without checking where the file needs to open.
• Deleting the original before confirming the conversion is exactly right.
• Accepting watermarks, signups or daily limits when free, unlimited tools exist.

The good news is that every one of these is easy to sidestep once you are aware of it. Take a moment to work from a good original, choose the right settings, and use a tool that keeps your files on your device, and the whole process becomes reliable rather than hit-or-miss. If something does not look right, it usually costs only a few seconds to adjust a setting and run it again — another advantage of doing everything instantly in your browser rather than waiting on a server round-trip.

Is it free and private?

Yes on both counts. The Video Compressor is completely free — no account, no subscription, no watermark and no cap on how many times you can use it. More importantly, it is private by design: the work happens inside your browser using your own device, so your files are never uploaded to a remote server. When you close the tab, nothing is left behind anywhere but on your own machine, which is exactly what you want when video compressor involves anything personal or confidential.

This is a genuinely different model from most "free" online tools, which upload your file to their servers, process it there, and ask you to trust that they delete it afterward. With a browser-based tool there is nothing to trust and nothing to delete, because your data never travelled anywhere in the first place. That is why ConvertProKit can offer these tools free forever without limits — there is no per-file server cost to recover — and why you can use them with sensitive documents and personal photos without a second thought.

Frequently asked questions

The bottom line

Getting a clip ready for Reels or TikTok is really two separate jobs — matching the vertical shape and length the platform expects, then getting the file size under its limit — and treating them as two distinct steps, trim then compress, is usually faster than trying to solve both at once.