ReactSync

Tracking since May 23, 2026.

Changelog

• Jun 5, 2026
  description

  v1.5.1
  
  • Tab A and Tab B selections no longer reset — your picks now survive closing the popup, minimizing the browser, or switching to another tab. Previously you had to re-pick both dropdowns every time the popup closed (unless sync was already active).
  • Auto-detect no longer hangs if a video pauses mid-capture — if either tab is paused during the 10-second audio capture, you now get a clear "keep both videos playing through the full 10s" message within ~13 seconds. Captures that complete at least 40% of the window still produce a result instead of erroring.
  
  ReactSync keeps a reaction video and its source video perfectly in sync across two browser tabs — automatically.
  
  Pick your reaction tab (Tab A) and your source tab (Tab B), enter the time offset between them, and hit Sync. From that point on, pressing play, pause, or seeking in either tab instantly mirrors the action in the other. No more manually pausing two videos every time you need a break.
  
  FEATURES
  
  • Automatic sync — play, pause, and seek events mirror across both tabs in real time
  • Time offset — set how many seconds Tab A leads Tab B (supports positive and negative values)
  • Nudge controls — fine-tune the offset in 0.5s, 1s, or 5s steps while watching
  • Keyboard shortcuts — Alt+Shift+Up / Down to nudge without opening the popup
  • Auto-detect offset — captures 10 seconds of audio from both tabs and uses cross-correlation to calculate the offset automatically (works on non-DRM content)
  • Audio source selector — hear Tab A only, Tab B only, or both
  • Survives tab reloads — sync resumes automatically once the video reloads
  • Persists across popup closes — your tabs and offset are restored when you reopen the popup
  • Dark and light mode
  
  COMPATIBILITY
  
  ReactSync works with any site that uses a standard HTML5 video element, including YouTube, Twitch, Vimeo, Patreon, and major streaming services. The auto-detect offset feature requires capturing audio and is unavailable on DRM-protected content.
  
  PRIVACY
  
  No data is collected, stored remotely, or transmitted to any server. All processing happens locally in your browser.

  ReactSync keeps a reaction video and its source video perfectly in sync across two browser tabs — automatically.
  
  Pick your reaction tab (Tab A) and your source tab (Tab B), enter the time offset between them (manually recommended), and hit Sync! From that point on, pressing play, pause, or seeking in either tab instantly mirrors the action in the other. No more manually pausing two videos every time you need a break.
  
  
  FEATURES
  • Automatic sync — play, pause, and seek events mirror across both tabs in real time
  • Time offset — set how many seconds Tab A leads Tab B (supports positive and negative values)
  • Nudge controls — fine-tune the offset in 0.5s, 1s, or 5s steps while watching
  • Keyboard shortcuts — Alt+Shift+Up / Down to nudge without opening the popup
  • Mark Sync Point — seek both videos to the same scene, click ⊙ A and ⊙ B, and the offset is calculated instantly. Works on every site including Netflix and Disney+
  • Auto-detect offset — captures 15 seconds of audio from both tabs and uses cross-correlation to calculate the offset automatically. Now includes a confidence check — if the audio doesn't match, you get a clear message instead of a wrong result (requires non-DRM content)
  • Audio source selector — hear Tab A only, Tab B only, or both
  • Survives tab reloads — sync resumes automatically once the video reloads
  • Persists across popup closes — your tabs and offset are restored when you reopen the popup
  • Dark and light mode
  
  
  COMPATIBILITY
  ReactSync works with any site that uses a standard HTML5 video element, including YouTube, Twitch, Vimeo, Patreon, and major streaming services. Mark Sync Point works universally. The auto-detect offset feature requires capturing audio and is unavailable on DRM-protected content (Netflix, Disney+, etc.).
  
  
  PRIVACY
  No data is collected, stored remotely, or transmitted to any server. All processing happens locally in your browser.

• May 29, 2026
  description

  ReactSync keeps a reaction video and its source video perfectly in sync across two browser tabs — automatically.
  Pick your reaction tab (Tab A) and your source tab (Tab B), enter the time offset between them, and hit Sync. From that point on, pressing play, pause, or seeking in either tab instantly mirrors the action in the other. No more manually pausing two videos every time you need a break.
  FEATURES
  • Automatic sync — play, pause, and seek events mirror across both tabs in real time
  • Time offset — set how many seconds Tab A leads Tab B (supports positive and negative values)
  • Nudge controls — fine-tune the offset in 0.5s, 1s, or 5s steps while watching
  • Keyboard shortcuts — Alt+Shift+Up / Down to nudge without opening the popup
  • Auto-detect offset — captures 10 seconds of audio from both tabs and uses cross-correlation to calculate the offset automatically (works on non-DRM content)
  • Audio source selector — hear Tab A only, Tab B only, or both
  • Survives tab reloads — sync resumes automatically once the video reloads
  • Persists across popup closes — your tabs and offset are restored when you reopen the popup
  • Dark and light mode
  COMPATIBILITY
  ReactSync works with any site that uses a standard HTML5 video element, including YouTube, Twitch, Vimeo, Patreon, and major streaming services. The auto-detect offset feature requires capturing audio and is unavailable on DRM-protected content.
  PRIVACY
  No data is collected, stored remotely, or transmitted to any server. All processing happens locally in your browser.

  v1.5.1
  
  • Tab A and Tab B selections no longer reset — your picks now survive closing the popup, minimizing the browser, or switching to another tab. Previously you had to re-pick both dropdowns every time the popup closed (unless sync was already active).
  • Auto-detect no longer hangs if a video pauses mid-capture — if either tab is paused during the 10-second audio capture, you now get a clear "keep both videos playing through the full 10s" message within ~13 seconds. Captures that complete at least 40% of the window still produce a result instead of erroring.
  
  ReactSync keeps a reaction video and its source video perfectly in sync across two browser tabs — automatically.
  
  Pick your reaction tab (Tab A) and your source tab (Tab B), enter the time offset between them, and hit Sync. From that point on, pressing play, pause, or seeking in either tab instantly mirrors the action in the other. No more manually pausing two videos every time you need a break.
  
  FEATURES
  
  • Automatic sync — play, pause, and seek events mirror across both tabs in real time
  • Time offset — set how many seconds Tab A leads Tab B (supports positive and negative values)
  • Nudge controls — fine-tune the offset in 0.5s, 1s, or 5s steps while watching
  • Keyboard shortcuts — Alt+Shift+Up / Down to nudge without opening the popup
  • Auto-detect offset — captures 10 seconds of audio from both tabs and uses cross-correlation to calculate the offset automatically (works on non-DRM content)
  • Audio source selector — hear Tab A only, Tab B only, or both
  • Survives tab reloads — sync resumes automatically once the video reloads
  • Persists across popup closes — your tabs and offset are restored when you reopen the popup
  • Dark and light mode
  
  COMPATIBILITY
  
  ReactSync works with any site that uses a standard HTML5 video element, including YouTube, Twitch, Vimeo, Patreon, and major streaming services. The auto-detect offset feature requires capturing audio and is unavailable on DRM-protected content.
  
  PRIVACY
  
  No data is collected, stored remotely, or transmitted to any server. All processing happens locally in your browser.

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