Loudness MeterLUFS, true peak and loudness range, to EBU R128.

Yes. Measure, normalize and export as many files as you like, with no account and no watermark.

No. Files are read and measured in your browser, and normalized files are made there too. Nothing is sent to a server.

It follows ITU-R BS.1770-4 and EBU R128: K-weighting, 400 ms blocks every 100 ms with the −70 LUFS and −10 LU gates, short-term loudness over 3 s, loudness range per EBU Tech 3342 and true peak with 4× oversampling (2× at 88.2 and 96 kHz). On the EBU test signals and on generated music, speech and noise at 44.1, 48 and 96 kHz, integrated loudness and loudness range agree with a reference meter to within 0.01 LU, and true peak of program material to within 0.1 dB.

Integrated loudness is the loudness of the whole file, ignoring silence and very quiet passages (gating). Short-term is the loudness of the last 3 seconds and momentary of the last 0.4 seconds; the graph shows both over time.

True peak is the highest level of the waveform including the peaks between samples that appear when the sound is converted or encoded. PLR is true peak minus integrated loudness, a measure of punch. Loudness range (LRA) is how much the loudness varies between the quieter and louder parts.

The file is turned up or down to the target. With “Gain + limiter”, a true-peak limiter with look-ahead holds peaks under the ceiling; the result is measured again and fine-tuned if needed so it lands within 0.1 LU of the target. With “Gain only”, the gain stops before any peak reaches the ceiling.

Yes. Files of several hours are read piece by piece, so they don't fill your memory; an hour of stereo usually takes under a minute. Mono, stereo, 5.0, 5.1 and 7.1 are supported: surround channels count +1.5 dB and the LFE channel is left out, as the standard says.

Yes. Measure a microphone or the sound of a browser tab (for example a video you are playing) in real time, with the same meters, then save a report.

It doesn't detect dialogue, so it can't give a dialogue-gated reading; it doesn't compress, EQ or edit the sound; and it saves the normalized sound as an audio file (to put back into a video, use your editor). Peaks of MP3 and AAC files can rise slightly in encoding; the measured result shows it.