Make a local capture
- Connect a supported source and start reception.
- Open the receiver’s Capture & replay panel and choose an available recording format.
- Press Start I/Q recording, then stop when you have captured the desired interval.
- Wait for preparation and request the download. Keep the binary and metadata together.
The format is fixed when recording starts. Stopping, reaching capacity, retuning, configuration changes or a source failure can complete the current segment. Preparation and a download request are separate states; a requested download does not prove the browser saved the files.
Understand the recording pair
| Source | Native I/Q | Export |
|---|---|---|
| RTL-SDR | CU8 | BrowserSDR binary + JSON, or SigMF |
| HackRF One / Pro | CI8 | BrowserSDR binary + JSON, or SigMF where supported |
| bladeRF 2.0 Micro | SC16 Q11, with /2048 replay scale | SigMF ci16_le with explicit Q11 provenance |
| USRP B205-mini | Losslessly reordered SC16 | SigMF ci16_le |
A SigMF pair contains .sigmf-data sample bytes and a .sigmf-meta metadata file. Metadata describes the sample rate, datatype and capture frequency, along with provenance and integrity information. A binary file without its matching metadata is not a complete recording.
Storage and downloads
When Origin Private File System storage is available, captures stream into private browser storage with an application limit of 2 GiB. A bounded 32 MiB memory fallback is used when that storage is unavailable. Browser quotas and available space can reduce the practical recording duration.
One prepared capture is retained up to the documented limit until discard or replacement. Captures up to 32 MiB of I/Q plus metadata can be requested as an uncompressed ZIP; larger captures use separate file downloads. Browser-storage captures remain in the local recording library across reload; interrupted captures recover only committed samples with an unknown missing tail. Delete retained captures explicitly and keep external backups: browser eviction and clearing site data can remove local recordings. Memory fallback captures must be downloaded before closing the tab.
Replay a saved signal
Select I/Q recording replay in Signal source and import a compatible binary/metadata pair. BrowserSDR restores the recording’s sample rate and capture center. Replay reads files up to 2 GiB in bounded chunks. Pause and resume during playback, or stop and change the start/end range to seek. Replay never asks for USB permission, and the recorded RF center cannot be moved as if the capture were live hardware.
Choose a mode compatible with the recorded bandwidth and datatype. Replay cannot recover signals outside the sampled RF window or turn a missing over-the-air signal into a valid decode. Preserve the originals if you export annotations or derived results.
Optional SigIntAtlas saving
The prepared SigMF pair can be saved to SigIntAtlas through the app’s opt-in authenticated workflow. That action transfers the selected capture and metadata; local processing alone does not upload radio data. Some formats have downstream analysis limits, including bladeRF Q11 captures where automatic analysis remains disabled until support is established.
For browser and radio setup, return to Getting started. See privacy details before sharing a recording or report.