LL-HLS playlist does not advertise CAN-BLOCK-RELOAD
Without blocking reload, players must poll for updates and the latency benefit is lost.
What it means
The playlist uses low-latency tags but its EXT-X-SERVER-CONTROL does not declare CAN-BLOCK-RELOAD=YES.
Why it matters
Blocking reload lets a player ask for the next version of the playlist and have the server hold the request open until it exists. Without it the player polls on a timer, so it learns about each new part up to a poll interval late — which is generally larger than the latency low-latency HLS was meant to remove.
How to fix it
- Add CAN-BLOCK-RELOAD=YES to EXT-X-SERVER-CONTROL.
- The origin must genuinely support blocking requests, holding the connection until the requested media sequence exists.
- Check your CDN passes blocking requests through rather than answering from cache.
Check your own stream
The free HLS analyzer runs this check on every analysis and links each finding straight back here.
Open the HLS analyzer →Frequently asked questions
- What does "LL-HLS playlist does not advertise CAN-BLOCK-RELOAD" mean?
- The playlist uses low-latency tags but its EXT-X-SERVER-CONTROL does not declare CAN-BLOCK-RELOAD=YES.
- Why does it matter?
- Blocking reload lets a player ask for the next version of the playlist and have the server hold the request open until it exists. Without it the player polls on a timer, so it learns about each new part up to a poll interval late — which is generally larger than the latency low-latency HLS was meant to remove.
- How do I fix it?
- 1. Add CAN-BLOCK-RELOAD=YES to EXT-X-SERVER-CONTROL. 2. The origin must genuinely support blocking requests, holding the connection until the requested media sequence exists. 3. Check your CDN passes blocking requests through rather than answering from cache.
- How can I detect this automatically?
- Paste your HLS streaming URL into StreamTest's free HLS analyzer. It runs this check on every analysis, flags the finding, and links straight back to this page — no sign-up required.
Related HLS checks
- HLS ladder has a bitrate inversionA lower-resolution variant is allocated more bandwidth than a higher-resolution one, so adaptive switching picks the wrong rendition.
- HLS variant is missing the CODECS attributeWithout CODECS, players must download a segment before they can tell whether they can play the rendition at all.
- HLS variant references an undeclared rendition groupA variant points at an AUDIO or SUBTITLES group that has no matching EXT-X-MEDIA entry, which breaks playback on strict players.
- HLS segment is longer than EXT-X-TARGETDURATIONA segment rounds to more than the declared target duration, which violates the HLS specification.
- HLS live window is shorter than three target durationsThe playlist holds too little content, so any player that falls slightly behind runs off the end of the window.
- HLS playlist has no EXT-X-PROGRAM-DATE-TIMEWithout program date-time the stream cannot be mapped to wall-clock time, which breaks DVR seeking and multi-stream alignment.