A Chrome Extension that measures the loudness (LUFS), True Peak and dynamic range of whatever is playing in a browser tab — live, in a side panel next to the page. It also analyzes audio files you drop into it, and can record the tab to a WAV file. Handy for checking your levels while recording.
- Live loudness metering of the current tab: Momentary, Short-Term and Integrated LUFS
- True Peak in dBTP with 4× oversampling, so inter-sample peaks are caught
- Dynamic range as LRA (EBU Tech 3342), plus PLR (Peak-to-Loudness Ratio)
- Runs in the Chrome side panel, so it stays open next to the page while you work
- The tab keeps playing audibly while it is being measured
- Measure: live metering, switchable between Simple (traffic-light verdicts — too quiet / just right / too loud, how much dynamics, whether it clipped) and Advanced (numeric values and bar meters with target markers)
- Optional live history graph of the last 60 seconds (Short-Term + Momentary)
- File: drop audio files anywhere in the panel (or click to pick them) for a full analysis — several at once queue up and are listed for comparison
- Three charts per report, on a shared time axis: Short-term loudness, True Peak with markers at every overshoot, and dynamic range (rolling LRA)
- Hovering any chart reads all three at that instant, with a synced crosshair
- Codec and bitrate read from the file itself, plus a collapsible panel with its title, artist, date and encoder
- Record: capture the tab to a 16-bit WAV, named after the tab and numbered so takes never overwrite each other
- Export the analysis report as PNG or PDF, or copy it as text
- Targets: Podcast (−16 LUFS), Streaming (−14 LUFS), Broadcast EBU R128 (−23 LUFS), None, or your own value
- Changing the target updates an existing report instantly, no re-analysis needed
- Reset button, plus an option to auto-reset when playback stops
- Files are decoded at their own sample rate, and the tab is captured at the stream's rate, so nothing is resampled before it is measured
- Info icons (ⓘ) next to every value explaining what it means
- German and English UI, follows your browser language
- Everything runs locally in the browser — no audio or data ever leaves your machine
Measurement follows ITU-R BS.1770-4 / EBU R128 (K-weighting, two-stage gating). The DSP runs in an AudioWorklet on the audio thread, so CPU load stays low.
This is an unpacked (developer) install.
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Download the repo: Code → Download ZIP, then unzip
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Open Chrome's Extensions page:
chrome://extensions -
Turn on Developer mode (top-right).
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Click Load unpacked and select the folder that contains
manifest.json. -
(Optional) Pin it: click the puzzle-piece Extensions icon → Pin.
Go back to chrome://extensions and click Reload on the extension card.
The folder must remain, once it is deleted, the extension will not work anymore.
Open the tab you want to measure, start playback, then click the LUFSly icon in the toolbar on that tab. The side panel opens and arms the capture; press Start to begin measuring.
That icon click is what grants Chrome's tab-capture permission, so it has to happen on the tab you want to measure. If you reload that tab, click the icon again. The Stop / Start button inside the panel pauses and resumes without needing another icon click.
Recording works the same way: arm the tab with the icon, switch to Record and press start — it connects the capture itself, so you do not need to start measuring first.
Browser-internal pages (chrome://, the Web Store, etc.) cannot be captured — switch to a normal website first.
 Measure · Simple — traffic-light verdicts |
 Measure · Advanced — values and meters |
 File — report with three charts and PNG/PDF export |
 Record — capture the tab to a WAV file |