No. Nobody reads the contents of your FLV, and nothing is shared. The uploaded FLV and the resulting MP3 are deleted from our servers automatically about 24 hours after the conversion, which leaves time to download the result.
Can I batch-extract audio from multiple FLV files?
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Several files in one job need a paid plan. Free use is one file per conversion, one conversion an hour. On a paid plan you can add several files to one job, then download each result on its own or all of them in one ZIP.