enableWorker defaults to true, but that setting alone does not make the hls.js ESM build use a worker. The ESM distribution does not bundle the transmuxer worker: configure workerPath to point to a deployed, version-matched hls.worker.js asset. Without it, transmuxing runs on the main thread. The UMD distribution handles this differently because its worker is inlined.
Why enableWorker: true may not be enough
hls.js has two relevant settings: enableWorker, which defaults to true, and workerPath, which defaults to null, according to the official API documentation. The first enables worker use when one is available; it does not provide a missing worker asset.
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The project’s README explains the distribution difference: hls.mjs does not bundle the transmuxer worker. In an ESM setup, if no worker path is configured, transmuxing stays on the main thread. The README’s guidance is explicit: “When using the ESM version of the library (hls.mjs), this option is required in order for web workers to be used.”
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →The worker’s documented role is TS demuxing and MP4 remuxing, also described as transmuxing. This does not mean all playback, network loading, or media decoding moves into a worker. The documentation presents improved performance and reduced lag or frame drops as goals, not guaranteed results or a published benchmark.
#1 Best Overall
- 【1080P HD High Quality】Capture resolution up to 1080p for video source and it is ideal for all HDMI devices such as PS4, PS3, Xbox One, Xbox 360, Wii U, DVDs, DSLR, Camera, Security Camera and set top box. Note: Video input supports 4K30/60Hz and 1080p120/144Hz. Does not support 4K120Hz/144Hz. Output supports up to 2K30Hz.
- 【Plug and Play】No driver or external power supply required, true PnP. Once plugged in, the device is identified automatically as a webcam. Detect input and adjust output automatically. Won't occupy CPU, optional audio capture. No freeze with correct setting.
- 【Compatible with Multiple Systems】suitable for Windows and Mac OS. High speed USB 3.0 technology and superior low latency technology makes it easier for you to transmit live streaming to Twitch, Youtube, Facebook, Twitter, OBS, Potplayer and VLC.
- 【HDMI LOOP-OUT】Based on the high-speed USB 3.0 technology, it can capture one single channel HD HDMI video signal. There is no delay when you are playing game live.
- 【Support Mic-in for Commentary】Rybozen capture card has microphone input and you can use it to add external commentary when playing a game. Please note: it only accepts 3.5mm TRS standard microphone headset.
First identify the build your application deploys
Do not infer the final distribution from a source-level import alone. A bundler can resolve and package a different artifact than the source syntax might suggest. The migration guide notes that bundlers such as webpack are likely to select ESM by default, and identifies workerPath as necessary for worker use with ESM starting with the 1.4 ESM distribution.
- ESM (
hls.mjs): the transmuxer worker is separate; pointworkerPathat the deployed worker file. - UMD: the worker is inlined, so the separate-worker-path issue specific to ESM does not apply in the same way.
These details are documented on the project’s mutable master branch. For a pinned or historical hls.js release, check the documentation and packaged files for that exact version rather than assuming current master describes it.
Rank #2
- 4K60 Capture: Record in cinematic quality with crisp detail and vivid colors
- HFR Support: Play and capture in 1440p120 or 1080p240
- HDR10 Support: Capture brilliant HDR content with tone mapping on Windows
- Cross-Platform Compatible: Works with PS5, Xbox Series X/S, Switch 2, and more
- Analog Audio In: Capture in-game chat or commentary with 3.5mm input
Configure the ESM worker asset
Set workerPath to a URL your application can serve, using the hls.worker.js asset that matches the hls.js version in use. The README gives this example:
const hls = new Hls({
workerPath: 'https://cdn.jsdelivr.net/npm/hls.js@1/dist/hls.worker.js',
});This is an example URL, not a universal deployment prescription. In your application, serve or reference the correct asset and keep its version aligned with the library. A configured value indicates intent; it does not prove the deployed URL resolves or that a worker starts.
Rank #3
- 【1080P 60FPS Video Capture Card】 This HDMI game capture card is based on USB3.0 high speed transmission port, input resolution up to 4K@30HZ, output resolution up to 2K@30Hz or 1920×1080@60Hz. Type c and USB interface can meet most of the devices in daily life. Easily meet the online capture, real-time recording, online meetings, live gaming and other functions, so you have a better visual enjoyment. Note: For capture use only; requires capture software to function and is not intended for direct screen casting to a monitor or TV
- 【Ultra Low Latency Screen Sharing】 HDMI capture card is made of good quality aluminum alloy with strong heat dissipation, allowing you to enjoy ultra low latency while live gaming or video recording or live streaming, avoiding blue screens and lag. This HDMI to USBC capture card supports easy recording of good quality audio or HD video and transferring it to your computer or streaming platform, allowing you to record 60 fps HD video directly on your hard drive and real-time preview
- 【Plug and Play, Easy to Carry】 This HDMI 1080P video capture card does not require any additional drivers or external power supply, just plug and play for fast capture. The capture card is small and lightweight, so you can put it in your bag for emergencies, making it very portable for outdoor live streaming. It's also a great way to share content in game recording, video conference, video recorder and online teaching
- 【Wide Compatibility USB Capture Card】 Easily streams to Facebook, Youtube or Twitch. With the connection, this HDMI to USB C/3.0 video capture devices can be working on several Operating Systems and various software: Windows 7/ 8/ 10, Mac OS or above, Linux, Android, Laptop, Xbox One, PS3/PS4/PS5, Camera, DVDs, Set Top Box, Webcame, DSLR, Switch/Switch 2, TV BOX, HDTV, Potplayer/VLC, ZOOM, OBS Studio etc.
- 【Package Content & Note】 1x HD Audio Capture Card , 1x USB 3.0 to USB C Adapter (A-side 3.0, B-side 2.0), 1x user manual. Please note that you need to restart the OBS Studio software after the audio setup is complete, otherwise it will result in no sound output. When using an adapter, if the device is recognized as USB 2.0, try using the other side with the USB-C port. Simply flip the capture card and reconnect it to be recognized as USB 3.0
Verify worker use in the deployed page
- Inspect the resolved build. Check the built application or dependency output to determine whether it includes the ESM or UMD distribution.
- Check the effective configuration. For ESM, confirm that
workerPathresolves to the intendedhls.worker.jsasset and that the versions match. - Observe the browser at runtime. Use the browser’s available developer tools to inspect network activity for the worker asset and whether a worker target appears or starts. Tool labels and views can differ, so report the observation you actually see rather than relying on a configuration value alone.
- Diagnose failures at the asset boundary. If the worker asset is missing or does not load, verify the deployed URL and that the corresponding file is being served. Until the ESM worker is available, transmuxing remains on the main thread.
What worker use changes—and what it does not establish
When available and enabled, the worker is for TS demuxing and MP4 remuxing. Its intended benefit is to reduce main-thread work that can contribute to lag or dropped frames. The official documentation does not provide a controlled benchmark or promise a specific improvement, so whether it helps a particular stream depends on the application and playback workload.
Quick Recap
Best Value
- 【4K Clarity, 1080P Performance】Enjoy stunning clarity with our USB 3.0 Video Capture Card—featuring 4K input and smooth 1080P@60Hz output. Featuring YUY2 technology, it delivers richer colors than MJPEG for lifelike live streaming and recording. Plus, it delivers high-quality video with minimal latency, making it perfect for gamers and content creators.
- 【Mic-in for Easy Commentary】Plug in a headset or mic directly to stream/record voice easily—no extra adapters. Great for real-time gaming commentary, online classes, or vlog dubbing. Paired with its low-latency tech, it keeps voice synced perfectly with video, eliminating post-editing hassle from mismatched audio-visuals. Fits most 3.5mm devices—ideal for gamers, teachers, creators.
- 【Plug and Play, no Extra-Drivers】No extra drivers or external power—just plug in and start capturing instantly. Small and lightweight, it fits easily in your bag for outdoor live streams, on-the-go recordings, or emergencies. Ideal for game capture, video conferences, and online teaching, it saves hassle while delivering smooth results.
- 【Wide Compatibility: Apps & Devices】No extra adapters—works flawlessly with your go-to platforms and gear. It pairs with streaming/recording apps like Twitter, YouTube, Facebook, OBS, XSplit, and VLC, plus devices including Switch/Switch2, PS5/PS4, Xbox, DSLR cameras, PC, macOS, and Android. Whether gaming, streaming, or hosting video calls, it keeps HD quality intact, eliminating "compatibility headaches".
- 【Worry-Free After-Sales Support】We are committed to delivering exceptional quality products that combine sophisticated design with affordable pricing, offering you the best solutions for seamlessly connecting your work and life. Whether you're a newcomer or a seasoned user, feel free to reach out anytime with any questions—your satisfaction is our top priority.
Rank #4
- High-Quality Video Capture, 4K HDMI Capture Card Ready: Capture smooth and vibrant video with this 4K HDMI capture card, engineered for gamers and content creators who demand crisp 1080P 60FPS video quality. Whether you're streaming to Twitch or recording gameplay for YouTube, your footage will look professional and detailed
- Plug-and-Play USB Capture Card, No Drivers Needed: Designed as a USB capture card for streaming, this device works instantly out of the box, just plug into your PC or laptop and start capturing. Fully compatible with popular software like OBS Studio, Streamlabs, and XSplit, making setup quick and stress-free for beginners and pros alike
- Universal Compatibility PS5, Xbox, Switch & More: Stream or record gameplay from virtually any HDMI-enabled device including Nintendo Switch, PS5, Xbox Series X, DSLR cameras, and PCs. The video capture card for gaming supports seamless passthrough so you can play without lag while your audience watches every frame in real time
- Low-Latency Performance for Smooth Streaming: This capture card for streaming minimizes delay between gameplay and broadcast, so you get reliable, low-latency capture that works well for competitive gaming, live broadcasts, and podcast sessions. Suitable for those building their channel with high-quality, engaging content
- Compact & Portable Design for Content Creators: Lightweight and portable, this USB 3.0 capture card works well for creators who travel or switch gaming setups often. Throw it in your bag and stream or record wherever you are, at home, events, LAN parties, streaming or studio sessions
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