On-device · Offline · Free
Big videos.
Small files.
Nothing leaves your phone.
Ninja compresses, converts and edits video entirely on your device. No server, no account, no upload — the Android app doesn't even request the Internet permission, so your phone enforces the promise for us.
Ninja Compress is a free video compressor app for iPhone and Android, made by Katani Labs. It compresses, converts and edits video entirely on your phone — nothing is uploaded to a server. You choose a target size or a preset for WhatsApp, Discord, email or social apps, compare the compressed video with the original side by side, and your original is only touched after the copy passes nine safety checks. The compressor is free with no ads, no account and no watermark; Ninja Pro is an optional upgrade. Ninja Compress is a mobile video app — it is not a desktop or image-compression program.
Free on the App Store as Ninja Video Compress & Convert (iPhone, iOS 15.0 or later) and on Google Play as Ninja Video Compressor (Android 8.0 or later).
- file
- Demo_Aurora_1080p.mp4
- before
- 66.3 MB
- after
- 11.5 MB
- saved
- 54.8 MB
- cut
- −83%
- No adsNot a banner, not a "watch this to continue".
- No watermarkFree or Pro, Ninja never stamps its branding on your video.
- No accountOpen it and go. There's nothing to sign into.
- No Internet permissionSo Android itself blocks Ninja from the network.
How it works
The whole thing, in 25 seconds.
A screen recording of the real app, edited for length.
- 01PickFrom your gallery — sorted by newest, largest or longest — or share a video in from any app.
- 02Choose how smallLeave it on Ninja Auto, or pick a size, a quality or a share preset. The estimate is live.
- 03Check, then keepCompare the result with the original at the same moment. Only then decide what happens to the original.
The Forge
Six ways to decide how small.
A live size estimate updates before you commit — so "how small" is a number you choose, not a surprise you discover. Want the math? Work out what bitrate fits your limit.
Ninja Auto
Reads each video's bitrate, resolution and codec, then picks the biggest saving that still looks sharp.
Quality
Five steps you can name: Extreme, High, Balanced, Small, Tiny.
Target size
"Fit this into 25 MB" — the one for attachments and upload caps.
Percentage
Aim each video at a share of its own size. Useful for a mixed batch.
Resolution
Pick the height, 2160p down to 240p; bitrate follows.
Manual bitrate
For when you already know the number.
Hardware encoders do the heavy lifting, so a 4K clip takes minutes, not an afternoon. If a phone's encoder refuses a file, Ninja steps down a four-rung fallback ladder and finishes in software instead of failing.
Share presets
Sized for where it's going.
Fifteen one-tap targets, each sized to fit its platform on file size, resolution and frame rate, so the file goes through the first time.
Messaging
- WhatsApp16 MB
- Telegram2 GB
- Discord20 MB
- Discord Nitro500 MB
- iMessage / MMS3.5 MB
- Gmail25 MB
- Outlook20 MB
- Yahoo Mail25 MB
Social
- Instagram Feed650 MB
- Instagram Reels650 MB
- Instagram Story650 MB
- TikTok287 MB
- YouTube Shorts2 GB
- X (Twitter)512 MB
- LinkedIn5 GB
Platforms move their limits. Our video compression guides for iPhone, WhatsApp, Discord and email track the current numbers, and Target size mode takes any number you type.
The verification gate
It will not delete the wrong thing.
Most compressors ask you to trust them with your originals. Ninja earns it: before an original can be touched, the compressed copy has to pass all nine checks, in this order. One failure and nothing is deleted — full stop.
- 01It existsOutput file exists and is larger than 4 KB
- 02It parsesContainer parses with at least one video stream
- 03Same lengthDuration within max(±0.75 s, ±1%) of the expected length
- 04Sane videoVideo stream has codec, width and height
- 05Audio survivedAudio stream present and decodable when expected
- 06Frames decodeFrames decode at start, middle and final keyframe
- 07In your galleryOutput registered in the media library and readable
- 08Actually smallerOutput is smaller than the original
- 09Finished cleanlyJob completed successfully and was not cancelled
Then you decide what happens to the original.
- Keep bothOriginal untouched.
- Move to Ninja VaultThe original moves to an in-app vault. Restore it any time until you empty it.
- Move to system TrashThe original moves to your phone's Trash (Recently Deleted on iPhone), restorable for 30 days.
- Replace originalThe compressed video takes the original's place, name and date — so your gallery timeline doesn't break.
- Delete permanentlyAndroid only: the original is gone immediately. This cannot be undone. (iPhone Photos always keeps deleted videos for 30 days, so the iPhone app doesn't offer it.)
One confirmation per batch. A ten-second undo. And a savings threshold that keeps both files when the saving wasn't worth it.
Toolbox
A full toolbox.
Fourteen tools — six free, eight with Ninja Pro. Watermarks are your text or your image; Ninja never stamps its own branding on your video.
- ConvertMP4 · MKV · WebM · MOV and more
- TrimCut the start and end
- Cut the middleProRemove sections, join the rest
- CropFree or 16:9 · 9:16 · 1:1 · 4:5 · 4:3 · 2.35:1
- MergeProJoin clips into one, in your order
- SpeedPro0.25× – 4×, pitch preserved
- ReverseProPlay it backwards, sound and all
- Rotate / Flip90° steps and mirror
- MuteStrip the audio track
- WatermarkProYour text or your image, nine positions
- SubtitlesProBurn in, or add a selectable track
- Extract audioProMP3 · M4A · WAV · FLAC · OGG
- Grab a frameScrub to a moment, save it as PNG or JPG
- GIF makerProPalette-optimized · dithering and loop count
Containers MP4 · MKV · MOV · WebM · AVI · WMV · FLV · 3GP · MPEG · TS · M4V · OGV
Codecs H.264 · H.265 / HEVC (Pro) · VP8 · VP9 (Pro) · AV1 (Pro) · MPEG-4
Built for real phones
Start a batch. Put the phone down.
- Keeps going in the background. A foreground service holds long jobs while you use other apps.
- Pause and resume straight from the notification.
- Minds the heat. If your phone gets hot, the queue pauses between files — and tells you why.
- Survives being killed. If the system closes Ninja mid-batch, it offers to resume what it lost.
- Share into it. Send a video to Ninja from any gallery or messenger.
- Remembers. Searchable history, in-app playback, and a same-timestamp before/after comparison.
Privacy, without the asterisk
A policy is a promise.
A missing permission is proof.
Any app can promise not to upload your videos. Ninja's Android build ships without theINTERNET permission, so the system refuses its network access before a single byte could leave. You don't have to take our word for it: the permission list is part of the app, readable with any APK inspector.
- No analytics. No crash reporting. No advertising ID. No sign-in.
- Your data stays in Ninja's private storage — history, presets and settings — and is erased when you clear app data or uninstall.
- When something breaks, Ninja writes it down on the phone. You decide whether to share that text — one tap, one time, into an app you choose.
- This website too. No cookies, no analytics, nothing loaded from anyone else.
Read the privacy policy — it's short, because there isn't much to say.
Before you install any compressor
Five questions worth asking.
Check the store listing's privacy section and the permissions list. Here's how Ninja answers.
Price
The compressor is free. Pro is the power tools.
No ads and no account either way. Pro is bought through Google Play or the App Store and checked on your phone, so it works offline too.
Free, forever
- Every size mode and all 15 share presets
- Up to 3 videos per batch
- Convert, trim, crop, rotate, mute, frame grab
- H.264, VP8 and MPEG-4
- Nine-check safe delete, the Vault and undo
- One saved preset
Ninja Pro
- Batches of any size
- Cut the middle, merge, speed, reverse, watermark, subtitles, extract audio, GIF maker
- H.265 / HEVC, VP9, AV1
- Unlimited saved presets
App Store: $2.99 / month · $14.99 / year · $29.99 onceGoogle Play: $0.99 / month · $5.99 / year · $14.99 once
US prices; the stores set local prices. Subscriptions renew until canceled in your store account. Terms
FAQ
Questions, answered plainly.
How do I compress a video on iPhone?
Re-encode it at a lower bitrate. Photos and iMovie can't target a file size, so use a compressor app: in Ninja, pick the video from your Photos library, and either leave it on Ninja Auto or choose Target size and type the size you need, such as 25 MB. The estimate shows the expected size before anything is encoded. After compressing, compare the result with the original at the same moment, then decide what happens to the original. Ninja is free on the App Store as Ninja Video Compress & Convert, for iPhone with iOS 15.0 or later.
How do I compress a video on Android?
Re-encode it at a lower bitrate. Gallery apps can trim a video but can't target a file size, so use a compressor app: in Ninja, pick the video from your gallery, and either leave it on Ninja Auto or choose Target size and type the size you need, such as 25 MB. The estimate shows the expected size before anything is encoded. After compressing, compare the result with the original at the same moment, then decide what happens to the original. Ninja is free on Google Play as Ninja Video Compressor, for Android 8.0 or later.
How do I send a video that is too large?
Either send the full file another way, or make the file smaller. On iPhone, AirDrop reaches nearby Apple devices and Mail Drop handles email attachments up to 5 GB. When the limit is at the other end, compress the video to fit: WhatsApp's Help Center lists 100 MB for video at 720p on faster connections and 64 MB at 480p on slower ones (sent as a document, up to 2 GB), Discord's free limit is 20 MB, and Gmail attachments stop at 25 MB. Ninja's share presets and Target size mode make the file fit on the phone, without uploading it.
Is Ninja free?
The compressor is, forever — every size mode, every share preset, trim, crop, rotate, mute, convert, frame grab and safe delete, with no watermark and no daily cap. Ninja Pro is optional: it adds batches of more than 3 videos, eight advanced tools, H.265 / VP9 / AV1 and unlimited presets, for App Store: $2.99 / month, $14.99 / year, $29.99 once; Google Play: $0.99 / month, $5.99 / year, $14.99 once (US prices; the stores set local prices). There are never ads.
Does Ninja Pro need an account or the Internet?
No account. You buy it through Google Play or the App Store, which handle the payment — Ninja never sees your payment details. The app checks your purchase with the store app on your phone, so Pro keeps working offline.
Does Ninja upload my videos anywhere?
No. Everything happens on your phone — there's no server, no account and no upload. The Android app doesn't even request the Internet permission, so the operating system itself blocks it from reaching the network.
Will compressing ruin the quality?
Ninja Auto reads each video's bitrate, resolution and codec and picks the biggest saving that still looks sharp. Before you keep anything, The Reveal lets you drag a divider across the original and the result at the same timestamp, and pinch in to check detail.
Could it delete the wrong file?
An original can only be touched after the compressed copy passes nine checks — it plays, it's the right length, its audio survived, frames decode at the start, middle and end, it's really in your gallery and really smaller. One failure and nothing is deleted. You also choose what happens to originals, including keeping both, and there's a ten-second undo.
Which formats does it handle?
12 containers — MP4, MKV, MOV, WebM, AVI, WMV, FLV, 3GP, MPEG, TS, M4V, OGV — with H.264, H.265 / HEVC, VP8, VP9, AV1, MPEG-4. H.265 / HEVC, VP9, AV1 come with Ninja Pro; the rest are free.
Does it work offline?
Entirely. Compressing, converting and editing never need a connection, so Ninja works the same in airplane mode, on a plane or with no signal at all. The one exception is buying or restoring Ninja Pro, which the store app does online; after that, Pro works offline too.
Is there an iPhone version?
Yes — Ninja Video Compress & Convert is on the App Store. It is built for iPhone; there is no iPad version.
Why is Reverse limited to one minute?
Reversing a video means holding every frame in memory at once. Past a minute, phones start to run out — and we would rather refuse than crash.
Your gallery is full of videos you'll never delete.
Make them small instead.