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If you’re a frontend developer working on video playback, you’re probably focused on startup time, smooth scrubbing, and adaptive bitrate tuning. But there’s one backend lever that quietly makes or breaks the viewing experience: CDN caching and purging.
Caching is why your streams load fast and reliably across regions. But if your cache holds onto outdated video segments or manifests, even the best player logic can’t save your users from glitches, stale content, or broken playback.
That’s where cache purging comes in clearing out the old, so your users always get the right content at the right time.
In this post, we’ll break down how CDN caching works in video streaming, why purging matters, and what every frontend developer should know to avoid caching-related playback issues.
Because even the smoothest UI can’t fix a bad cache.
A Content Delivery Network (CDN) is a globally distributed network of servers that delivers content to users based on their geographic location. Instead of routing every request back to a single origin server, a CDN caches copies of your content at edge servers closer to where your users actually are.
For video streaming, this isn’t just a nice-to-have it’s used for reducing latency, improving startup time, and keeping buffering to a minimum.
Here’s how it typically works:
The result: less waiting, fewer playback interruptions, and a better overall experience for your audience, no matter where they’re watching.
To know more on CDN, check out our content on CDNs (Content Delivery Networks) for video streaming.
Most modern video streaming protocols, like HLS (HTTP Live Streaming) and DASH (Dynamic Adaptive Streaming over HTTP), don’t deliver one giant video file. Instead, they break the stream into smaller pieces making playback adaptive, efficient, and cache-friendly.
Here’s what’s happening under the hood:
When user hits play, the video player:
If those segments are already cached at the nearest edge server, they’re delivered almost instantly. If not, the CDN pulls the segment from the origin, caches it at the edge, and then serves it to the player.
This approach keeps playback fast and responsive but it also means that cache freshness directly impacts what your users see on screen.
Caching your video segments at the edge is what makes playback feel fast and responsive. But caching comes with a catch — what happens when the content changes?
Imagine these common scenarios:
Without proper cache purging, your users might:
Cache purging (or cache invalidation) fixes this by removing the outdated segments from the CDN cache, forcing the next request to pull the fresh content from your origin.
The result:
While cache purging is critical for both on-demand and live streaming, live streaming introduces unique caching and purging challenges due to its real-time nature. Let’s explore these considerations in detail.
Caching for live streaming isn’t the same as caching on-demand video. With VOD, your playlists and segments are relatively static they don’t change once the file is encoded and uploaded. But live streaming is a moving target. Playlists update every few seconds. New segments are generated continuously. And what’s cached at the edge needs to stay tightly in sync with what’s happening at the origin.
This introduces a few unique challenges:
Short cache lifetimes, frequent updates: In live workflows like HLS or DASH, the media playlist is updated regularly to point to the newest segments. If the cache holds onto an old version of that playlist for too long, your viewers won’t see the latest chunks which can lead to buffering, lag, or even playback stalls.
To avoid this, live playlists typically use a very short cache TTL (time-to-live). For example, setting Cache-Control: max-age=5 ensures the playlist gets refreshed every five seconds, keeping the player aligned with the stream in real time.
The risk of stale segments and broken playback: If the edge cache holds onto outdated segments especially after a live event ends users might still request video chunks that no longer exist on the origin. This often results in 404 errors or failed playback attempts.
When and why purging matters for live streams: Purging becomes critical at two key points in a live workflow:
With FastPix APIs, you can automate purging workflows directly within your live streaming pipeline ensuring that playlists and segments are always up to date without relying on manual cache-busting or reactive fixes.
If you’re working on a video player, you might not be the one managing CDN configurations directly. But caching and knowing when to purge it plays a huge role in how your playback performs. Outdated segments, stale playlists, or broken metadata can all surface as playback issues that, from the outside, look like player bugs.
Understanding how caching works (and what to watch for) helps you build a more reliable streaming experience and makes troubleshooting much faster when things break.
Here’s what frontend developers need to keep in mind about CDN caching and purging for video playback.
In most HLS or DASH video streams, the following files are cached by the CDN:
When a stream is updated whether it's a new video version, added captions, or corrected segments these cached assets might need to be purged to prevent stale content from reaching your users.
Not all playback failures are caused by the player code. Sometimes, the problem is that the CDN is still serving an outdated or missing segment.
Most video player libraries (like HLS.js) let you listen for error events that can hint at caching problems. For example:
javascript
player.on(Hls.Events.ERROR, function (event, data) {
if (data.details === 'manifestLoadError' || data.details === 'fragmentLoadError') {
console.warn('Potential cache issue with segment or playlist');
}
});
If you’re seeing manifestLoadError or fragmentLoadError, the player might be requesting segments or playlists that no longer exist — a common sign of stale cache.
In critical situations where you need to bypass the cache (like urgent content updates), you can add a cache-busting query parameter to your video URL. This forces the CDN to treat the request as unique and fetch fresh content:
javascript
player.loadSource(`https://cdn.example.com/stream/playlist.m3u8?nocache=${Date.now()}`);
But be cautious cache-busting impacts performance by skipping the CDN’s cache. Use it only when necessary.
Some scenarios require more than just cache-busting they call for an actual purge of cached content. Common cases include:
Many CDN providers offer APIs to purge specific paths or files. Here’s a simple example of how a purge request might look:
javascript
await fetch('/api/cdn/purge', {
method: 'POST',
body: JSON.stringify({ path: '/stream/video123/*.ts' }),
});
Automating purges at the end of a live stream or when content is updated helps keep your playback clean without relying on manual intervention.
Keeping your video playback smooth isn’t just about encoding settings or player logic — how you handle caching and purging at the CDN level makes a big difference. Here are a few best practices to avoid stale content and ensure a reliable streaming experience:
Set cache headers intentionally: Use proper Cache-Control headers to guide how your CDN handles caching. Specify max-age, stale-while-revalidate, or similar directives to control how long playlists, segments, and metadata stay cached at the edge.
Purge caches when content changes: Always purge cached playlists or segments when a video is updated, replaced, or a live stream ends. This ensures viewers aren’t stuck with outdated manifests or broken chunks.
Monitor and handle playback failures gracefully: Watch for errors related to missing segments or manifest files especially 404 responses. Use player-side error handling to retry requests when possible or surface clear error messages to the user instead of leaving them with a stalled player.
Track your cache performance: Keep an eye on your cache hit ratio and segment load times. A consistently low cache hit ratio might mean your caching rules are too aggressive or misaligned with your playback patterns. Adjust your TTLs and purging strategy as needed.
Caching improves video performance but without proper security, it can also expose your streams to unnecessary risks. Whether you’re purging outdated segments or controlling access to sensitive content, how you secure your CDN setup matters.
Here are key security practices to keep your caching and purging workflows safe and reliable:
Always secure purge requests: CDN purge APIs should never be open to the public. Require authentication for any purge action using API keys, OAuth tokens, or signed headers. For example, a purge request might include:
http
Authorization: Bearer <your-token>
This prevents unauthorized requests from clearing your cache or disrupting your streams.
Use signed URLs or short TTLs for sensitive content: For private or premium video content, use signed URLs that expire after a short window — or apply short cache lifetimes (max-age) to reduce exposure. This ensures that only authorized users can access the content, even if it’s cached at the edge.
Avoid caching sensitive assets unless required: If you’re dealing with private streams or user-specific content, avoid caching it altogether unless there’s a clear need. Use to prevent the CDN from keeping copies of sensitive segments, playlists, or metadata.
http
Cache-Control: no-store
Monitor for abuse and unusual patterns: Watch your CDN logs for spikes in purge requests or unusual cache behaviors. Repeated or excessive purge calls can be a sign of abuse, misconfiguration, or even an attempted denial-of-service (DoS) attack on your caching layer.
Caching is one of those things that works quietly in the background—until it doesn’t.
Outdated playlists, stale segments, missing metadata… these aren’t player bugs. They’re often the result of cache drift between your origin and the edge.
You can patch these issues manually: purge the CDN, tweak TTLs, add cache-busting parameters. But at some point, scaling a streaming product becomes less about fighting fires and more about choosing the right infrastructure that helps you avoid them altogether.
That’s where FastPix fits in.
FastPix provides video APIs built to simplify the hard parts of streaming from video processing to delivery. Whether you're managing on-demand libraries, live events, or hybrid workflows, FastPix gives you the flexibility to control how your content is served without needing to duct-tape together encoding logic, delivery pipelines, and caching layers yourself. So, you can focus on building the product your viewers care about. Not chasing down the last stale segment. Explore our feature page to know more on our offering.
Stale CDN caches can continue serving outdated .vtt subtitle files or chapter metadata even after you’ve updated them. This means viewers may miss newly added captions or navigation points unless the relevant cached assets are purged, causing a disconnect between what’s updated on the origin and what users see.
Typical signs include sudden playback stalls, lag despite stable internet, or 404 errors for segments. These often result from stale media playlists or expired segments still being served from the edge cache after the origin has moved on.
No. Cache-busting bypasses the cache by changing the request URL (usually with a query param), forcing a fresh fetch. Cache purging, on the other hand, actively deletes specific cached content from edge servers, ensuring old content is no longer served to any users.
To clear CDN cache after updating a video, you need to use your CDN provider’s purge API or dashboard. Target specific paths—like playlist or segment URLs—to ensure only the outdated video assets are removed without impacting other cached content.
This usually happens because the CDN is still serving a cached version of the video. Until the cached segments and playlists are purged or expire based on TTL settings, viewers may continue seeing stale content despite your updates.
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