Bluesky Video Dimensions
The recommended Bluesky video size is 1280 × 720 pixels at a 16:9 horizontal aspect ratio. This is HD resolution that plays cleanly on every device and fits comfortably under the 50 MB file cap at standard bitrates.
720p (HD) is the sweet spot on Bluesky. 1080p works but eats your file budget, at the 50 MB cap, 1080p forces low bitrates that make compression artifacts visible. 720p at 5,000 kbps looks sharper on a phone screen than 1080p at 3,000 kbps.
Supported aspect ratios
| Ratio | Pixel Size | Feed Behavior |
|---|---|---|
| 16:9 (horizontal) | 1280 × 720 px | Default, no letterbox in feed preview |
| 9:16 (vertical) | 720 × 1280 px | Letterboxed in feed; full-screen on tap |
| 1:1 (square) | 720 × 720 px | Side-letterbox in feed preview |
The 50 MB File Size Cap
Bluesky caps video uploads at 50 MB. Like the 1 MB image limit, this is a protocol-level cap from the AT Protocol, every server in the federation has to store and replicate the file, so smaller is better network-wide.
To fit a 60-second 720p clip under 50 MB:
- Resolution: 1280 × 720 px
- Codec: H.264 (AVC), High profile
- Bitrate: 5,000 kbps (constant or two-pass)
- Frame rate: 30 fps
- Audio: AAC, 48 kHz, 128 kbps stereo
That math: 5,000 kbps × 60 s = 300,000 kbits ≈ 37.5 MB video, plus ~1 MB audio = ~38–40 MB total. Comfortable margin under the 50 MB cap.
Bitrate vs. quality trade-off
| Length | Bitrate | Approx. File Size | Quality |
|---|---|---|---|
| 60 sec | 3,000 kbps | ~24 MB | Visible compression |
| 60 sec | 5,000 kbps | ~38 MB | Good, recommended |
| 60 sec | 6,500 kbps | ~50 MB | Best, at file cap |
| 30 sec | 10,000 kbps | ~38 MB | Excellent for short clips |
Codec & Format Specifications
- Container: MP4 (preferred), MOV, or WebM
- Video codec: H.264 / AVC (universal). HEVC / H.265 is not supported.
- Audio codec: AAC at 48 kHz, 128 kbps stereo minimum
- Frame rate: 30 fps recommended; 24 fps and 60 fps also work
- Color space: Rec. 709 / sRGB
- Profile: H.264 High profile, level 4.0 or 4.1
Why Videos Look Compressed
Unlike Instagram or Threads, Bluesky doesn't aggressively re-encode uploads, what you upload is roughly what plays back. The flip side: a poorly-encoded original looks poorly on Bluesky too. To get the cleanest playback:
- Use two-pass H.264 encoding, squeezes 10-15% better quality at the same bitrate
- Don't exceed 30 fps unless the source is genuinely 60 fps motion
- Avoid sharp scene cuts at low bitrates, keyframes get expensive and compromise nearby frames
- Render at 720p not 1080p, at 50 MB cap, 720p almost always looks better
Tips for High-Quality Bluesky Videos
- Default to 1280 × 720 H.264 MP4 at 5,000 kbps for 60-second clips
- Use AAC audio at 128 kbps stereo
- Keep videos under 60 seconds, that's the hard cap
- Two-pass encode for best quality / size ratio
- Don't use HEVC / H.265, it's not supported
- Add a transcript or caption in alt text for accessibility, Bluesky supports up to 2,000 characters
- Need exact 16:9 cropping for video posters? Try our X (Twitter) sizing tools.
Frequently Asked Questions
What is the best video size for Bluesky?
The best video size for Bluesky is 1280 × 720 pixels at a 16:9 horizontal aspect ratio. This is full HD that fits comfortably under the 50 MB file cap at typical bitrates, and matches the format Bluesky displays in feed previews.
How long can a Bluesky video be?
Bluesky videos can be up to 60 seconds long. There is also a daily upload quota, accounts that post many videos in a short window may hit a temporary cap and need to wait before uploading again.
What is the maximum file size for a Bluesky video?
Bluesky enforces a 50 MB file cap on video uploads. To stay under it: export 1280 × 720 H.264 at roughly 5,000 kbps with AAC audio at 128 kbps. A 60-second clip at those settings lands around 40 MB.
What aspect ratios does Bluesky video support?
Bluesky video supports 16:9 (horizontal, 1280 × 720), 9:16 (vertical, 720 × 1280), and 1:1 (square, 720 × 720). The feed displays video in a 16:9 preview by default, vertical clips are letterboxed in feed and play full-screen on tap.
What video format and codec should I use for Bluesky?
Use MP4 with H.264 video and AAC audio at 48 kHz. WebM with VP9 is also accepted and can be smaller, but support is less universal, when in doubt, use MP4/H.264.
How do I keep a 60-second video under 50 MB?
Export at 1280 × 720 (not 1080p) using H.264 at 5,000 kbps with AAC audio at 128 kbps. That yields ~40 MB for 60 seconds. If you need 1080p, drop bitrate to ~6,000 kbps and shorten clips to 45 seconds. Two-pass H.264 encoding squeezes another 10-15% out at the same quality.
Can I post horizontal video on Bluesky?
Yes, horizontal 16:9 is the default and looks best in the feed preview. If your source is vertical, you can either letterbox it to 16:9 or upload vertical (720 × 1280) and accept the smaller feed preview.
Why does my Bluesky video upload fail?
Most failures are caused by exceeding 50 MB or the 60-second length cap. Other causes: unsupported codec (HEVC/H.265 is not accepted), corrupted file, or hitting a daily upload quota. Re-export to MP4 H.264 at 1280 × 720, 5,000 kbps to fix most issues.