Compress Video Online — Free, No Upload

How it works

Drop your video
Any common format, any size. Nothing is uploaded — the tool runs in your browser.
Pick a size
Drag the slider — the estimated output shows live — or set an exact size in MB, like Discord's 10 MB.
Download
Hardware-accelerated compression fits your video under the target — guaranteed.

How the compressor decides

Type a size and the tool turns it into a bit budget: target bytes times eight, divided by duration. Pass one hands the encoder 93% of it, because containers cost bytes and hardware encoders overshoot. Audio takes a fixed slice — 128 kbps when the total is 1.5 Mbps or more, stepping to 96, 64 and 48 kbps as targets tighten — and video gets the rest. If video's share would fall under 80 kbps, audio is dropped instead of shipping smear, and the result says so.

Resolution is kept while the video bitrate can sustain 0.045 bits per pixel per frame. Below that, the tool steps down a fixed ladder — 2160, 1440, 1080, 720, 540, 480, 360, 240 — never upscales, and reports the new dimensions. Under a 10 MB target, a 30-second clip typically keeps 1080p or 720p; around two minutes, expect 480p-class output.

The target is a promise, so the tool checks its own work. Pass one usually lands 5–13% over; the encode is rerun with a compounding correction, up to three passes, and pass two almost always fits. If even the 80 kbps floor cannot fit, it refuses — “Try a larger target size or trim the video first.” — rather than hand back a broken file. A file already under the target is returned untouched.

The slider is a different mode: one fast pass, no size guarantee, in three zones — Light, Balanced, Strong. Across it the ceiling falls from 0.14 to 0.025 bits per pixel per frame, capped relative to the source (85% of its own bitrate at the gentlest setting, 22% at the harshest), so an encode never spends more than the original carries. Light is deliberately restrained: it steps down at most one rung (1080p may become 720p, never 480p), and a source already spending under half of Light's budget comes back byte-for-byte unchanged with an honest note. Fat iPhone footage still compresses. Under Balanced and Strong, an in-memory output landing more than 1.5× the live estimate is redone in exact-size mode, aimed at the estimate.

Two engines, both on your device. WebCodecs uses your video hardware and runs first, preferring H.264 because it is the one codec that plays everywhere — which is why an MKV or a WebM comes out as an MP4. When the browser cannot read the container (AVI, FLV, WMV, 3GP, MPG) or has no WebCodecs, as in older Firefox builds, the same job runs on an ffmpeg.wasm fallback — software instead of video hardware, still no upload.

Which size do you actually need?

Most compression is done to clear a cap somebody else set. The numbers below are the ones each platform documents — the linked page carries the presets and the fine print — and where no byte cap is published, the table says so instead of inventing one.

Platform	Documented cap	What catches people
Discord	10 MB free · 50 MB Nitro Basic · 500 MB Nitro	Checked to the byte; follows the uploader’s subscription, not the server.
WhatsApp	Status 16 MB; chats accept far larger	Status clips beyond 30 seconds are split; big chat videos get re-compressed hardest.
Email	Gmail and Yahoo 25 MB, Outlook.com 20 MB — advertised	Base64 inflates attachments ~33%: practical ceilings about 18 MB (Gmail) and 15 MB (Outlook); corporate servers commonly 10 MB.
Telegram	2 GB (4 GB with Premium)	Send as a file to preserve it exactly; 50–100 MB sends in seconds.
Messenger	25 MB chat media · 100 MB as a file attachment (mobile)	The file path has no inline playback — the recipient downloads.
WeChat	Chat video under 20 MB	Photos 10 MB; in-app recordings 15 seconds; no published send-as-file cap, so none is printed.
Slack	1 GB per file, every plan	Free plan: files leave view after 90 days, deleted after one year — retention, not size.
KakaoTalk	300 MB per file, phone and PC alike	Every file type; no paid tier raises it.
Zalo	1 GB per file	Media at or under 100 MB is kept long-term; heavier media can expire.
Twitter (X)	512 MB and 2 min 20 s (standard accounts)	MP4 or MOV; Premium allows more, but X re-encodes every upload.
Instagram	No byte cap printed — presets 25 MB Story · 50 MB Reel · 100 MB long video	Re-encodes every upload; oversized files get squeezed hardest.
TikTok	Web: under 10 GB and 30 min · API/scheduler 4 GB · Ads Manager 500 MB	The app documents duration (60 min), not bytes; the “287 MB iPhone limit” is on no official page.
YouTube	256 GB or 12 hours (15 minutes until phone-verified)	Recommended ~8 Mbps at 1080p, 5 Mbps at 720p — bytes above are mostly discarded.

Two patterns do most of the damage. Email measures the encoded message, not your file, so the email page targets 18 MB for Gmail and 15 MB for Outlook rather than the advertised 25 and 20. And chat apps run two lanes — Messenger's 25 MB inline versus 100 MB as a file, WhatsApp's 16 MB Status versus far larger chats. For a cap no platform page covers, the size pages run from 2 MB through 8 MB, 25 MB and 100 MB up to 200 MB.

Trim first, then compress

When the tool refuses a target, its message ends with “trim the video first”, and it means it: a tight one-minute clip at 10 MB almost always looks better than ten minutes crushed into the same budget. Trim video opens a real player; cutting only the end of an H.264 file copies the stream without re-encoding, and moving the start (or any other codec) re-encodes frame-accurately on your video hardware. Crop video snaps to 9:16, 1:1, 16:9 or 4:3 first, so only the pixels you keep spend bitrate. Formats a browser will not play — AVI, WMV, often old-phone 3GP or broadcast TS — get no preview in either tool: convert them to MP4 first. If you only need the sound, skip compression and extract the MP3. And compress once: repeated re-encoding compounds quality loss, so run your final target on the original.

Frequently asked questions

Is my video uploaded to a server?

No. ConvertUno runs entirely in your browser using your own device’s hardware. Your video never leaves your computer or phone — there is no upload, which is also why there is no waiting for one.

Is it really free, with no watermark?

Yes. Because compression happens on your device, serving you costs us almost nothing — so there is no watermark, no account, no file-size limit, and no daily quota.

Will the quality drop a lot?

The compressor spends your size budget as efficiently as possible: it keeps resolution when the bitrate allows it and only scales down when that is the better trade for watchable quality. Small targets for long videos will always look softer — that is physics, not the tool.

Which formats can I compress?

MP4, MOV, WebM, MKV and legacy formats (AVI, FLV, WMV, MPG) are accepted. The output is an MP4 (H.264) file that plays everywhere — Discord, WhatsApp, email clients, TVs.

Why does the exact size matter?

Platforms enforce hard caps — Discord rejects a file even 1% over its 10 MB free limit. ConvertUno treats your target as a promise: the output is guaranteed to fit under it.

What do Light, Balanced and Strong actually do?

They set how much of the source’s own bitrate survives — 85% at the gentlest setting, 22% at the harshest — under a ceiling that falls from 0.14 to 0.025 bits per pixel per frame. Light keeps 128 kbps audio and steps resolution down at most one rung; Strong uses 96 kbps audio and steps as far as the budget requires. None of the three guarantees a byte count — for that, set an exact size.

Why did it return my file unchanged?

Two honest reasons. In exact-size mode, a file already under the target is handed back untouched — compressing toward a budget must never grow a file. On Light, a source already spending under half of Light’s bits-per-pixel budget (a screen recording, a lean download) can only lose quality from a re-encode, so it comes back byte-for-byte with a note. Switch to Balanced or set an exact size to shrink it anyway.

Can it compress a 2 GB file?

Yes — there is no input size limit, because the file is read from your disk, not uploaded. In Chromium browsers a single file of 300 MB or more asks where to save first, then writes the result straight to disk as it encodes, so memory stays flat; other browsers run the job in memory, and the tool warns you first when the file is large for your device. A hardware-accelerated pass typically runs near real-time speed.

Compress to an exact size

Compress video to 2 MB Squeeze a video under 2 MB right in your browser — for forum attachments, chat embeds and strict form uploads. Free, private, guaranteed to fit.
Compress video to 8 MB Shrink any video to under 8 MB in your browser — no upload, no watermark, free. Perfect for strict upload forms and Discord's classic 8 MB limit.
Compress video to 10 MB Compress any video to under 10 MB right in your browser. Free and private with no upload — made for Discord's free limit and other strict caps.
Compress video to 16 MB Get any video under 16 MB in your browser — free, no upload, no watermark. The classic WhatsApp status limit and a common attachment cap.
Compress video to 20 MB Compress any video to under 20 MB in your browser — the classic Outlook attachment cap and a common portal limit. Free, private, guaranteed fit.
Compress video to 25 MB Compress a video to under 25 MB in your browser — free, private, no upload. Built for upload forms, course portals, and inbox caps, with a Gmail-safe preset.
Compress video to 50 MB Fit any video under 50 MB right in your browser — free, no upload, no watermark, no size limit on the input. Discord Nitro Basic's exact cap.
Compress video to 100 MB Compress any video to under 100 MB in your browser — free, private, no upload. Ideal for web uploads, portfolios, and sharing long recordings.
Compress video to 200 MB Bring a large video under 200 MB in your browser — course platforms, job portals and CMS upload caps. Free, private, no size limit on input.

Compress for a platform

Compress video for Discord Fit any video under Discord's 10 MB free limit (or 50 MB / 500 MB Nitro tiers) right in your browser. Free, private, no watermark, guaranteed to fit.
Compress video for WhatsApp Compress videos for WhatsApp in your browser — free and private, no upload. Beat the 16 MB Status limit and stop WhatsApp from wrecking your quality.
Compress video for email Compress a video so it actually sends by email — Gmail-safe 18 MB and Outlook-safe 15 MB presets that survive attachment encoding. Free, no upload.
Compress video for WeChat Fit videos under WeChat's 20 MB chat-video cap right in your browser — free, private, no upload, guaranteed to send.
Compress video for Messenger Fit videos under Messenger's 25 MB chat-media cap, or 100 MB as a file attachment — compressed in your browser. Free, private, guaranteed fit.
Compress video for Instagram Compress video for Instagram in your browser — free, private, no upload. Stop Reels and Stories from coming out blurry after Instagram re-encodes them.
Compress video for Telegram Compress videos for Telegram in your browser — free, private, no upload. Not for the 2 GB cap, but for instant sends and streaming that actually works.
Compress video for Twitter (X) Compress video for Twitter/X in your browser — free, private, no upload. Fit the 512 MB / 2:20 limits and survive X's re-encode with quality left.
Compress video for Slack Fit screen recordings under Slack's 1 GB per-file cap — or far smaller so channels stay fast. Compressed in your browser, free, private, no upload.
Compress video for Zalo Fit videos under Zalo's 1 GB file cap — or under 100 MB so Zalo Cloud keeps them long-term. Compressed in your browser, free and private.
Compress video for KakaoTalk Fit any video under KakaoTalk's 300 MB per-file cap right in your browser — free, private, no upload, guaranteed to send.
Compress video for TikTok Shrink videos for TikTok uploads in your browser — fit the 500 MB ads cap, the 4 GB scheduler cap, or just upload faster. Free, private.
Compress video for YouTube Shrink videos to YouTube's own recommended bitrates so uploads finish in minutes, not hours — compressed in your browser, free, no upload wait.

Compress by format

Compress MOV files Compress huge MOV files from iPhone or Mac right in your browser — free, private, no upload. Outputs a small MP4 that plays absolutely everywhere.
Compress MP4 files Compress MP4 files to any target size in your browser — free, private, no upload, no watermark. Hardware-accelerated and guaranteed to hit your size.
Compress WebM files Compress WebM screen recordings and clips in your browser — free, private, no upload. Outputs a compact MP4 that plays everywhere WebM does not.
Compress MKV files Compress MKV files in your browser — free, private, no upload, no input size limit. Turns bulky MKV videos into compact MP4s that play anywhere.
Compress AVI files Compress old AVI videos in your browser — free, private, no upload. Ancient camcorder files become small modern MP4s that play on today's devices.

Compress video to an exact size