CogniShield

Protect your eyes and brain while watching videos — blue light filter, flash guard, and volume limiter for YouTube.

CogniShield is a lightweight Chrome extension that silently protects you and your family while watching YouTube videos. It applies three real-time protections directly to the video — no content blocking, no data collection, and no interruptions. BLUE LIGHT FILTER Shifts the video color temperature toward warmer tones to reduce blue light exposure. Blue light (400-490 nm) is known to suppress melatonin and contribute to eye strain, especially in children whose eyes transmit more short-wavelength light. Adjust the intensity from subtle warmth to a deep amber tone. FLASH & FLICKER GUARD Continuously analyzes video frames for rapid brightness changes that could be harmful to photosensitive viewers. When flashing content is detected, CogniShield automatically dims the video to a safe level. The detection algorithm follows WCAG 2.3.1 guidelines and triggers conservatively — well below the threshold known to cause photosensitive reactions. VOLUME LIMITER Caps audio output to prevent sudden loud sounds from exceeding safe listening levels. Uses a professional-grade dynamics compressor to smooth out audio spikes before they reach your ears. Especially important for children, whose smaller ear canals amplify certain frequencies by an additional 5-10 dB compared to adults. AUTO-DETECT MODE Turn on Auto-Detect and CogniShield will analyze the video content in real time, automatically calibrating the optimal protection levels every 5 seconds. You can still fine-tune any slider manually at any time. WHO IS IT FOR? - Parents who want safer screen time for their children - People with photosensitive epilepsy or migraine triggers - Anyone who experiences eye strain from prolonged video watching - Night-time viewers who want to reduce blue light before sleep WHAT COGNISHIELD DOES NOT DO - Does not block, filter, or restrict any video content - Does not collect any personal data or browsing history - Does not communicate with any external servers - Does not require an account or sign-up - Does not affect any websites other than YouTube All your settings are stored locally on your device and never leave your browser. Changes apply instantly — no page reload needed.