NeuroShield

Real-time photosensitivity protection for the web. NeuroShield detects and blocks flashing, strobing, and dangerous visual patterns across ALL websites — not just YouTube. Protecting people with epilepsy, migraines, and visual snow syndrome. 3% of people with epilepsy have photosensitive seizures triggered by visual stimuli. Over 1 billion people live with migraines. Visual Snow Syndrome affects 2-3% of the population. Every existing flash detection tool only works on YouTube. The rest of the web — social feeds, news sites, ads, games — is unguarded. NeuroShield works everywhere. HOW IT WORKS NeuroShield samples video frames at 15 fps, downscaled to 32x32 pixels for performance. Each frame is analyzed using sRGB linearization (IEC 61966-2-1) and ITU-R BT.709 relative luminance — the same math the WCAG spec mandates. A sliding 1-second window counts opposing luminance transitions. If the delta exceeds 0.1 and the darker state is below 0.80 relative luminance, it counts as a flash. Three or more flashes per second (at default sensitivity) triggers a protective overlay. Region-based spatial analysis divides each frame into a 4x4 grid, checking 16 independent zones. This catches localized strobes — like a flashing ad in one corner — that whole-frame averaging would miss. Cross-origin videos where pixel analysis is blocked by browser security get an opt-in protective CSS filter instead. SENSITIVITY LEVELS Low — only extreme strobing (5+ flashes/sec) Medium — WCAG 2.3.1 standard (3+ flashes/sec) [default] High — for migraine and VSS sufferers (2+ flashes/sec) Maximum — full protection, any significant flash (1+ flash/sec) FEATURES - Real-time flash detection using WCAG 2.3.1 luminance thresholds with sRGB linearization - Works on every website — not just YouTube - Region-based spatial analysis catches localized flashes - Red flash detection per WCAG 2.3.2 (high seizure risk) - Warning overlay with Dim, Pause, and Continue controls - Protective CSS filter fallback for cross-origin videos - Accessible overlay: ARIA roles, keyboard navigation (Escape to dismiss), screen reader support - Starts at document_start — protects before any content renders - Resilient: survives extension updates and service worker restarts - Sensitivity from WCAG standard (3 Hz) down to maximum protection (1 Hz) WHEN A FLASH IS DETECTED A dark overlay immediately blocks the dangerous content. You get three options: Dim — reduces brightness to 30%, keeps video playing Pause — stops the video entirely Continue — dismisses the warning if you choose to proceed The overlay supports keyboard navigation and screen readers. Press Escape to dismiss. PRIVACY NeuroShield runs entirely on your device. Period. - Zero data collection - Zero network requests - Zero analytics or tracking - Zero accounts required - Only stores your sensitivity preference locally using Chrome storage All visual analysis happens in memory and is never saved, logged, or transmitted anywhere. Full privacy policy: https://github.com/OMARVII/Neuroshield/blob/main/PRIVACY.md TECHNICAL DETAILS - Chrome Extension Manifest V3 - WCAG 2.3.1 (Level A) and 2.3.2 (Level AAA) compliant - ITU-R BT.709 relative luminance calculation - IEC 61966-2-1 sRGB linearization - 84 unit tests, zero external dependencies - Open source: https://github.com/OMARVII/Neuroshield - MIT License PERMISSIONS EXPLAINED Storage: saves your sensitivity preference locally on your device. Content script access (all URLs): required to inject the flash detection engine into webpages — it only analyzes visual luminance of media elements, never reads page content, form data, cookies, or personal information. WHO THIS IS FOR - People with photosensitive epilepsy - Migraine sufferers sensitive to visual stimuli - People with Visual Snow Syndrome (VSS) - Parents protecting children from flashing content - Anyone who finds strobing content uncomfortable - Accessibility professionals testing web content Made by Omar Khaled https://www.omar-khaled.com