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Overview

HLS (HTTP Live Streaming) is an HTTP-based adaptive streaming protocol that can be delivered through standard CDN infrastructure. If your live streams or videos are in HLS format, Gcore CDN can proxy them to end users worldwide, significantly improving loading times and scalability. HLS works seamlessly with CDN because it’s based on HTTP—the same protocol used for regular static files. This means HLS content can be cached and distributed via CDN edge servers just like images or CSS files.

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When to use HLS via CDN

Use Video CDN for HLS if:
  • You already have HLS streams (.m3u8 playlists and .ts segments)
  • You handle transcoding on your side
  • You need global delivery at scale
  • You want CDN features like geo-blocking, secure tokens, or origin shielding
Use Video Streaming Platform if:
  • You have raw video input (RTMP, SRT, MP4) that needs transcoding → Use Video Streaming instead
  • You need automatic ABR (Adaptive Bitrate) ladder generation → Use Video Streaming instead

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Requirements

To use HLS streaming via CDN, you must meet these conditions:
  • HLS format: Your content must be in HLS format (.m3u8 playlists and .ts or .m4s segments)
  • Paid CDN plan: Any paid subscription
  • Legal approval: Streaming activation from Gcore support (see below)
Need transcoding? If your stream is in another format (RTMP, SRT, MP4) or you need automatic quality ladder generation, use the Video Streaming platform instead of Video CDN.

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Quick setup

For detailed step-by-step instructions on setting up HLS streaming via CDN, follow our comprehensive guide: Create a CDN Resource for Video Streaming This guide covers:
  • Requesting streaming activation from support
  • Creating and configuring your CDN resource
  • Setting up cache rules for optimal HLS delivery
  • Enabling the LIVE STREAMING preset
  • Testing your stream

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Low-Latency HLS (LL-HLS) Support

Gcore CDN fully supports LL-HLS (Low-Latency HLS) delivery for ultra-low latency streaming (2-4 seconds glass-to-glass latency).

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What is LL-HLS?

LL-HLS is an extension to the HLS protocol that enables sub-second latency by:
  • Using smaller segment chunks (partial segments)
  • Implementing HTTP/2 push and blocking playlist requests
  • Delivering segments as they’re being produced

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Supported file formats

File TypeExtensionDescription
Playlists.m3u8Master and media playlists with LL-HLS directives
Video segments.m4s, .m4vFragmented MP4 (fMP4) CMAF segments
Audio segments.m4a, .m4sAudio-only CMAF segments
Initialization.mp4Initialization segments for fMP4 streams

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Configuration requirements

To enable LL-HLS on your CDN resource:
  1. Enable query parameter whitelisting in your CDN resource cache settings
  2. Add these required LL-HLS query parameters:
    • _HLS_msn - Media Sequence Number for blocking playlist requests
    • _HLS_part - Partial segment number
    • _HLS_skip - Skip older segments in playlist response
  3. Set appropriate cache times:
    • Playlists (.m3u8): 1-2 seconds
    • Segments (.m4s, .m4v): 60 seconds or match your target latency
Detailed configuration: See the “Optional: LL-HLS (Low-Latency) configuration” section in the Getting Started Guide.

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Technical deep dive

For video engineers and CTOs interested in how Gcore achieves 3-second latency: Engineering blog post: Optimizing HLS and DASH for 3-second latency This article covers HTTP Chunked Transfer Encoding, HTTP/2 framing optimizations, and the technical implementation behind our low-latency streaming.

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Advanced cache configuration

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Understanding HLS cache behavior

HLS streaming works through two types of files that need different cache strategies: Playlists (.m3u8):
  • Contain metadata and the ordered list of video segments
  • Browsers request playlists first
  • Should be cached for 1-2 seconds to ensure viewers get the latest segment list
  • If cached too long, viewers receive outdated playlists pointing to non-existent segments
Segments (.ts or .m4s):
  • Contain actual video/audio data in small chunks
  • Browsers request segments in the order listed in the playlist
  • Should be cached for 60 seconds (longer than segment duration)
  • Longer cache protects slow-connection users from 404 errors when segments rotate

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Cache configuration methods

You can set cache TTLs in two ways:
  1. On your origin server: Use Cache-Control HTTP headers
  2. In Gcore Customer Portal: Create cache rules (see Getting Started Guide)
Cache settings for HLS

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Additional recommendations

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Origin shielding

If you expect more than 1K concurrent viewers, enable Origin Shielding to:
  • Reduce origin requests by 80-95%
  • Protect your origin from traffic spikes
  • Improve cache hit ratios

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Custom domains

Use custom domains for branded streaming URLs:
  • Before: http://123456.gcdn.co/playlist.m3u8
  • After: http://video.yourdomain.com/playlist.m3u8

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Testing your stream

Test HLS playback using:
  • VLC Media Player: Download VLC
  • Online players: HLS.js demo, JW Player demo
  • Mobile: Safari (iOS), Chrome (Android)

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Next steps

Getting Started Guide

Complete setup instructions for HLS streaming

Low-Latency MPEG-DASH

Alternative: LL-DASH for low-latency streaming

Video CDN Overview

All Video CDN features and capabilities

Engineering Blog

Technical deep dive: 3-second latency optimization