A Chrome MV3 extension for language learning on Netflix playback pages. It shows a second official subtitle track on top of the native one, so you can watch with two languages at the same time.
Native Japanese subtitle (top) with the MultiSubtitle Chinese overlay (bottom).
The extension captures Netflix timed text metadata available to the current
playback session, parses TTML/DFXP/VTT subtitle documents, and renders a
selectable subtitle overlay synchronized with the page <video> current time.
This is a feasibility MVP, not a production browser extension.
Netflix playback page
-> page-world hook observes fetch / XMLHttpRequest / parsed manifest data
-> extension identifies timed text tracks and subtitle document URLs
-> background worker fetches subtitle documents with the current browser session
-> parser converts TTML / DFXP / VTT into timed segments
-> content script renders the selected subtitle language above the native subtitle area
The native Netflix subtitle can stay on one language, while the extension overlay can display another available official subtitle track, such as English or Chinese.
- Chrome MV3 unpacked extension.
- Captures timed text track candidates from Netflix playback data.
- Parses common TTML, DFXP, and VTT subtitle formats.
- Lets the popup select a target overlay subtitle language.
- Caches fetched subtitle segments per video and language during the page session.
- Clears video-scoped subtitle state when the Netflix watch id changes.
- Keeps runtime diagnostics inside the popup details panel instead of the video overlay.
- Open Chrome
chrome://extensions. - Enable Developer mode.
- Click Load unpacked.
- Select this project directory.
- Open a Netflix playback page.
- Open the extension popup and choose a target subtitle language.
If you update the source files, reload the extension in chrome://extensions
and refresh the Netflix tab.
Install optional development dependencies:
npm installRun parser and syntax checks:
npm run checkRun parser tests only:
npm testThe smoke test launches a separate Chrome profile and loads this extension. The
first run requires manual Netflix login in the opened browser. The profile is
saved under .test-profile/, which is ignored by Git.
npm run test:netflixYou can pass a playback URL:
npm run test:netflix -- "https://www.netflix.com/watch/81502828"The script prints page state, popup state, and extension console logs every few seconds.
This project is intended for personal language learning and technical research.
It does not:
- bypass Netflix login, subscription, region, DRM, or playback authorization;
- decrypt media or subtitle payloads outside the browser session;
- download or persist subtitle files;
- redistribute Netflix content or subtitle text;
- provide any Netflix API compatibility guarantee.
Netflix is a trademark of Netflix, Inc. This project is not affiliated with, endorsed by, or sponsored by Netflix.
- Netflix playback internals are private and can change without notice.
- Track discovery depends on data visible to the active browser playback session.
- Subtitle availability depends on the selected title, region, account, and Netflix UI state.
- The parser covers the subtitle formats seen during this MVP; more adapters may be needed.
- The overlay is tuned for current Netflix desktop playback UI and may need layout adjustments.
GNU Affero General Public License v3.0 or later (AGPL-3.0-or-later).
You are free to use, modify, and distribute this project, including for commercial purposes. In return, any distributed or network-deployed derivative must also be released under the AGPL-3.0 and make its complete source code available to its users. See LICENSE for the full terms.
SPDX-License-Identifier: AGPL-3.0-or-later
这是一个用于 Netflix 播放页语言学习的 Chrome MV3 扩展。它在原生字幕之上叠加 显示第二条官方字幕轨,让你可以同时用两种语言观看。
Netflix 原生日文字幕(上)与 MultiSubtitle 中文叠加层(下)。
上方截图就是效果:Netflix 原生日文字幕保留在上方,MultiSubtitle 把中文字幕叠加 在下方。
扩展会读取当前播放会话可见的 Netflix 时间轴文本(timed text)元数据,解析
TTML/DFXP/VTT 字幕文档,并渲染一个与页面 <video> 当前时间同步的、可选择语言的
字幕叠加层。
这是一个可行性验证版(MVP),而非生产级浏览器扩展。
Netflix 播放页
-> 页面世界(page-world)钩子监听 fetch / XMLHttpRequest / 已解析的 manifest 数据
-> 扩展识别时间轴文本轨道与字幕文档 URL
-> 后台 worker 用当前浏览器会话拉取字幕文档
-> 解析器把 TTML / DFXP / VTT 转换成带时间戳的字幕片段
-> 内容脚本把所选语言的字幕渲染在原生字幕区域上方
Netflix 原生字幕可以保持一种语言,扩展叠加层则可显示另一条可用的官方字幕轨, 例如英文或中文。
- Chrome MV3 未打包(unpacked)扩展。
- 从 Netflix 播放数据中捕获候选的时间轴文本轨道。
- 解析常见的 TTML、DFXP、VTT 字幕格式。
- 在弹窗(popup)中选择目标叠加字幕语言。
- 在页面会话期间,按视频和语言缓存已拉取的字幕片段。
- 当 Netflix watch id 变化时,清除该视频维度的字幕状态。
- 把运行时诊断信息放在弹窗的详情面板里,而不是叠加在视频上。
- 打开 Chrome 的
chrome://extensions。 - 开启「开发者模式」。
- 点击「加载已解压的扩展程序」。
- 选择本项目目录。
- 打开一个 Netflix 播放页。
- 打开扩展弹窗,选择目标字幕语言。
如果你修改了源码,需要在 chrome://extensions 重新加载扩展,并刷新 Netflix 标签页。
安装可选的开发依赖:
npm install运行解析器与语法检查:
npm run check仅运行解析器测试:
npm test该测试会启动一个独立的 Chrome 配置目录并加载本扩展。首次运行需要在打开的浏览器里
手动登录 Netflix。配置目录保存在 .test-profile/,已被 Git 忽略。
npm run test:netflix也可以传入一个播放页 URL:
npm run test:netflix -- "https://www.netflix.com/watch/81502828"脚本会每隔几秒打印页面状态、弹窗状态和扩展控制台日志。
本项目仅用于个人语言学习与技术研究。
它不会:
- 绕过 Netflix 的登录、订阅、地区、DRM 或播放授权;
- 在浏览器会话之外解密媒体或字幕数据;
- 下载或持久化保存字幕文件;
- 转发 Netflix 内容或字幕文本;
- 提供任何 Netflix API 兼容性保证。
Netflix 是 Netflix, Inc. 的商标。本项目与 Netflix 无任何隶属、背书或赞助关系。
- Netflix 播放内部机制是私有的,可能随时变更。
- 轨道发现依赖于当前浏览器播放会话可见的数据。
- 字幕可用性取决于所选片名、地区、账号以及 Netflix 界面状态。
- 解析器只覆盖本 MVP 期间见到的字幕格式,可能需要更多适配器。
- 叠加层针对当前 Netflix 桌面端播放界面调校,可能需要调整布局。
GNU Affero 通用公共许可证 v3.0 或更高版本(AGPL-3.0-or-later)。
你可以自由使用、修改和分发本项目,包括商业用途。作为交换,任何被分发或部署为 网络服务的衍生作品,也必须以 AGPL-3.0 发布,并向其用户提供完整源代码。完整条款见 LICENSE。
SPDX-License-Identifier: AGPL-3.0-or-later