ThunderFox - Loudness Normalizer by 7nihilate

ThunderFox is a lightweight Firefox extension that applies loudness maximization to media elements (audio and video) on web pages.

This add-on may not work on websites that stream DRM controlled content.

Features:
- Multiband processing (Low / Mid / High) using linear-phase FIR bandpasses when supported, with biquad fallbacks.
- Parallel upward and downward compression inside each band to both raise low-level content and control peaks.
- Global highpass filter (user-toggleable) placed after band summing and before the limiter to remove sub-bass frequencies if desired.
- Final limiter with threshold control and automatic gain compensation so lowering the threshold increases output gain to approach 0 dB peaks.
- Persistent controls in the popup: enable/disable processing, toggle highpass, and adjust limiter threshold.