Everything it does,
and exactly how.

Share presets

Each preset carries a size target and resolution and frame-rate ceilings for its platform.

Preset	Size cap	Max height	Max fps
WhatsApp	16 MB	720p	30
Telegram	2 GB	1080p	—
Discord	20 MB	720p	—
Discord Nitro	500 MB	1080p	—
iMessage / MMS	3.5 MB	480p	—
Gmail	25 MB	1080p	—
Outlook	20 MB	1080p	—
Yahoo Mail	25 MB	1080p	—
Instagram Feed	650 MB	1080p	30
Instagram Reels	650 MB	1920p	30
Instagram Story	650 MB	1920p	30
TikTok	287 MB	1920p	60
YouTube Shorts	2 GB	1920p	60
X (Twitter)	512 MB	1080p	—
LinkedIn	5 GB	1080p	—

Caps are the values each preset targets in the app. Platforms change their limits; the guides track the current numbers, and Target size takes any value you type — or calculate a bitrate for any size limit.

Formats

H.264, VP8 and MPEG-4 are free; H.265 / HEVC, VP9, AV1 come with Ninja Pro. H.264 and HEVC encode through your phone's hardware encoders. Ninja's FFmpeg build contains no x264, x265 or xvid — see open source for why.

Tools

Fourteen of them — six free, eight with Ninja Pro. Watermarks are your text or your image — Ninja never adds its own.

• Convert

  MP4 · MKV · WebM · MOV and more

• Trim

  Cut the start and end

• Cut the middlePro

  Remove sections, join the rest

• Crop

  Free or 16:9 · 9:16 · 1:1 · 4:5 · 4:3 · 2.35:1

• MergePro

  Join clips into one, in your order

• SpeedPro

  0.25× – 4×, pitch preserved

• ReversePro

  Play it backwards, sound and all

• Rotate / Flip

  90° steps and mirror

• Mute

  Strip the audio track

• WatermarkPro

  Your text or your image, nine positions

• SubtitlesPro

  Burn in, or add a selectable track

• Extract audioPro

  MP3 · M4A · WAV · FLAC · OGG

• Grab a frame

  Scrub to a moment, save it as PNG or JPG

• GIF makerPro

  Palette-optimized · dithering and loop count

Free batches take up to 3 videos and keep one saved preset. Ninja Pro removes both limits. Prices.

Your originals

An original can't be moved, replaced or deleted until the compressed copy passes every one of these, in order. There's no partial credit.

1. 01
   It existsOutput file exists and is larger than 4 KB
2. 02
   It parsesContainer parses with at least one video stream
3. 03
   Same lengthDuration within max(±0.75 s, ±1%) of the expected length
4. 04
   Sane videoVideo stream has codec, width and height
5. 05
   Audio survivedAudio stream present and decodable when expected
6. 06
   Frames decodeFrames decode at start, middle and final keyframe
7. 07
   In your galleryOutput registered in the media library and readable
8. 08
   Actually smallerOutput is smaller than the original
9. 09
   Finished cleanlyJob completed successfully and was not cancelled

Then, one of five outcomes — your choice, per batch or as a default:

Keep both

Original untouched.

Move to Ninja Vault

The original moves to an in-app vault. Restore it any time until you empty it.

Move to system Trash

The original moves to your phone's Trash (Recently Deleted on iPhone), restorable for 30 days.

Replace original

The compressed video takes the original's place, name and date — so your gallery timeline doesn't break.

Delete permanently

Android 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 — 20% by default — below which both files are kept regardless of what you chose.

Reliability

Background jobs

A foreground service keeps long batches running while you use other apps.

Pause and resume

From the notification, or in the app.

Thermal pause

If the phone gets hot, the queue pauses between files and tells you why.

Resume after a kill

If the system closes Ninja mid-batch, it offers to pick up what it lost.

Share into Ninja

Send a video from any gallery or messenger straight into Ninja.

History

Searchable, with in-app playback and a same-timestamp before/after comparison.

Privacy

No analytics, no crash reporting, no advertising ID, no sign-in. The Android app doesn't request the Internet permission, so the system itself keeps it offline. When something goes wrong, the log stays on your phone until you choose to share it. The full policy.

Details

Themes

Dark and light — both hand-tuned rather than inverted, and contrast-checked.

Languages

English, Español, Português, Deutsch, Français, हिन्दी, Bahasa Indonesia, 日本語, Русский, 한국어, Italiano, Nederlands, Svenska, Norsk bokmål, Dansk, Suomi, 简体中文, 繁體中文, Polski, Türkçe, Tiếng Việt, ไทย, Українська, Čeština, Bahasa Melayu, العربية, עברית, Ελληνικά, Română, Magyar, Slovenčina, Hrvatski, Català.

Where results go

Your gallery, next to the original, or a folder you choose.

An honest limit

Reverse is capped at one minute: it holds every frame in memory, and we'd rather refuse than crash.