Features

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Detection and intake

HLS Downloader provides multiple ways to capture HLS streams:

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Automatic HLS sniffing

The extension monitors web requests in real-time and automatically detects HLS playlists:

• Background listener watches for .m3u8 content types
• Captures unique playlists per tab with page title and initiator details
• No manual DevTools inspection required
• Works as soon as you open a page with HLS content

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Toolbar feedback

When a playlist finishes parsing, the extension updates the toolbar icon for that specific tab to signal that a new capture is available for download.

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Direct URL entry

Manually add playlists that weren’t automatically detected:

• Paste any .m3u8 playlist URL in the Direct tab
• Creates a playlist entry without network sniffing
• Useful for JavaScript-loaded streams or manual capture
• Added playlists are parsed and available immediately

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Playlist parsing and selection

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Master playlist parsing

The extension fully parses HLS master manifests to extract all available streams:

• Retrieves master manifests and level playlists
• Extracts video renditions with bitrate, resolution, and FPS metadata
• Discovers audio renditions with language, bitrate, and channel information
• Sorts streams from highest to lowest quality
• Shows all technical metadata in the UI

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Subtitle and closed caption detection

Discovers and exposes subtitle tracks alongside audio and video:

• Parses SUBTITLES and CLOSED-CAPTIONS media groups
• Shows language, name, and characteristics for each track
• Downloadable as separate .vtt files
• Optional selection (subtitles can be skipped)

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Level filtering

Only successfully parsed playlists appear in the UI:

• Failed or incomplete parses are filtered out
• Playlists move to “ready” state after successful parsing
• Ensures all displayed playlists are downloadable

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Quality selection

Full control over which streams to download:

• Pick one video rendition from all available qualities (240p to 4K)
• Choose a separate audio rendition when available
• Optionally select subtitle or closed caption tracks
• View technical metadata for informed selection

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Metadata visibility

Detailed information for each stream level:

• Full URIs for video, audio, and subtitle playlists
• Resolution (width × height)
• Bitrate in mbps
• Frame rate (fps)
• Audio language codes
• Channel count (e.g., 2ch, 6ch)
• Default and auto-select flags

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Download pipeline

The extension implements a robust multi-stage download pipeline:

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Fragment discovery

Once you start a download, the extension:

• Fetches level playlists for selected video and audio streams
• Enumerates all fragments with absolute URLs
• Identifies initialization segments when present
• Builds a complete fragment list for download

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Resilient fetching

Downloads are optimized for speed and reliability:

• Configurable parallelism (concurrency) balances speed and stability
• Each fragment supports retry attempts (configurable in Settings)
• Failed fragments are automatically retried
• Progress tracking shows completed vs. total fragments

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Decryption

Built-in support for encrypted streams:

• AES-128 encrypted fragments are automatically detected
• Decryption keys and IVs are extracted from playlists
• Web Crypto API performs decryption locally in your browser
• No external services or uploads required

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Local storage buckets

All downloaded data stays in your browser:

• Video and audio fragments are written to IndexedDB
• Buckets are keyed by job ID for isolation
• Nothing is uploaded to external servers
• Data remains private and local

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FFmpeg-based muxing

The extension uses ffmpeg.wasm to merge streams:

• Runs entirely in your browser tab via WebAssembly
• Concatenates and muxes audio + video fragments into MP4
• Supports video-only or audio-only cases gracefully
• No server-side processing required

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Offscreen support for MV3

Chromium-based browsers using Manifest V3:

• Creates an offscreen document for blob URL generation
• Prevents service worker blocking
• Ensures smooth download triggering

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Save flow

Final step to get your video:

• Uses browser Downloads API to save the MP4
• Honors your save dialog preference from Settings
• Automatically uniquifies filenames to avoid conflicts
• Filenames are generated from page title and metadata

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Subtitle export

When a subtitle or closed caption track is selected:

• Fetches the subtitle playlist
• Concatenates segments into a single .vtt file
• Saves via the browser Downloads API
• Saved separately from the video file

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User interface modules

The extension popup is divided into functional tabs:

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Sniffer tab

Manage detected playlists:

• Lists all playlists detected from the current page
• Filter by title, URL, or initiator
• Copy all playlist URLs to clipboard
• Clear all detected playlists
• Drill into individual playlists to select tracks
• Manual URL input for direct playlist addition

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Direct tab

Alternative interface for manual playlist management:

• Accepts manual playlist URLs
• Lists resulting parsed entries
• Selection and download workflow

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Playlist view

Track selection interface:

• Shows available video, audio, and subtitle levels
• Dropdown selectors for each track type
• Displays technical metadata for informed choices
• Copy buttons for stream URLs
• Download button to start the job

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Downloads tab

Monitor and manage download jobs:

• Shows active and finished jobs
• Progress bars and percentage indicators
• Status badges (queued, downloading, ready, error)
• Job actions (cancel, delete, retry, save as)
• Filter to search through download history

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Settings tab

Configure extension behavior:

• Active downloads: Limit concurrent jobs (1-10 or unlimited)
• Fragment concurrency: Parallel fragment fetches
• Fetch attempts: Retry count per fragment
• Save dialog: Toggle save location prompt
• Preferred audio language: Auto-select audio by language code

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About tab

Extension information and links:

• Version number
• Quick links to GitHub issues, source code, privacy policy, and license
• Contribution information

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Persistence and cleanup

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Config persistence

Your settings are saved across sessions:

• Concurrency settings
• Fetch attempt configuration
• Save dialog preference
• Preferred audio language
• Stored in extension storage and restored on startup

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Bucket cleanup

Automatic storage management:

• Startup cleanup epic runs when extension loads
• Clears IndexedDB buckets based on cached metadata
• Prevents stale storage accumulation
• Keeps your browser clean

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Non-persistence of jobs and playlists

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Build and compatibility

The extension supports multiple browsers and manifest versions:

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Manifest variants

• MV2: For Firefox and legacy Chromium workflows
• MV3: For modern Chromium-based browsers (Chrome, Brave, Edge, Arc, Opera)
• MV3 uses offscreen documents for blob URL creation

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Browser coverage

Verified to work on:

• Firefox (via Firefox Add-ons or manual install)
• Google Chrome (manual install, experimental)
• Microsoft Edge (via Edge Add-ons)
• Brave (manual install)
• Arc (manual install)
• Opera (manual install)
• Other Chromium-based browsers

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Cross-platform support

Works on Windows, macOS, and Linux with any supported browser.

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Privacy and security

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100% local processing

All operations happen in your browser:

• Fragment downloads go directly to your device
• Decryption uses local Web Crypto API
• FFmpeg runs via WebAssembly in your tab
• No data is uploaded to external servers

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No tracking or telemetry

The extension does not collect any usage data, analytics, or personal information.

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Minimal permissions

Required permissions are limited to:

• webRequest and webRequestBlocking: Detect HLS playlists
• tabs: Associate playlists with the correct tab
• downloads: Save MP4 files to your device
• storage: Persist settings and configuration