MP3 to FLAC Converter
Convert MP3 to FLAC online for free. Fast, secure, and high-quality conversion with no sign-up or software required.
Maximum file size is 1GB
How it works
Three steps to your converted file
Everything happens in your browser tab - upload, pick a format, download. The heavy lifting runs on our servers.
Upload your file
Drag and drop, click to browse, or paste a URL. Batches take up to 20 files at once - 230+ input formats across video, audio, image, document, and archive types.
Choose an output format
Pick from over a hundred output formats. Filter by category or search by name - every option is open to everyone, no account needed.
Convert & download
Hit Convert and grab your download link moments later. Originals are erased when the job completes; results are cleared within about an hour.
What is an MP3 file?
MPEG-1 Audio Layer III (MP3) is a lossy audio compression format defined by ISO/IEC 11172-3, developed by the Fraunhofer Institute. It uses perceptual coding based on psychoacoustic models to discard auditory data deemed imperceptible to the human ear, specifically utilizing the Modified Discrete Cosine Transform (MDCT) and Fast Fourier Transform (FFT). The format structures data into frames consisting of a header and data block, becoming the de facto standard for digital audio transfer in the 1990s.
How to open an MP3 file
MP3 playback is universally supported across all major operating systems (Windows, macOS, Linux, Android, iOS) without requiring additional codec installation. Native applications such as Windows Media Player, QuickTime, and Groove Music handle the format by default. Advanced users seeking spectral analysis or tag editing may utilize Audacity or Mp3tag.
MP3 Technical Info
- Full Name
- MPEG-1 Audio Layer III
- Developed By
- Fraunhofer Society
- Initial Release
- 1993
- MIME Type
- audio/mpeg
What is a FLAC file?
The Free Lossless Audio Codec (FLAC) is an open-source audio coding format developed by the Xiph.Org Foundation that compresses digital audio without any loss of data (bit-perfect preservation). It employs linear prediction and Rice coding (Golomb-Rice) rather than the perceptual psychoacoustic modeling used in MP3 or AAC. The format structure consists of the 'fLaC' stream marker, metadata blocks (Streaminfo, Vorbis comments for tags, Seekpoints), and audio frames, typically achieving compression ratios of 50-70% compared to raw PCM WAV files.
How to open a FLAC file
FLAC enjoys extensive native support on modern platforms, including Windows 10/11, Android, and macOS (starting with macOS High Sierra). For older systems or advanced playback control, software such as Foobar2000 (Windows) or Vox (macOS) is recommended. The VLC media player is a universal solution for all operating systems, handling FLAC streams and associated metadata seamlessly.
FLAC Technical Info
- Full Name
- Free Lossless Audio Codec
- Developed By
- Josh Coalson / Xiph.Org Foundation
- Initial Release
- 2001
- MIME Type
- audio/flac
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Why RunConvert
The fastest way to convert any file
Purpose-built for speed, privacy, and breadth of format support.
Convert MP3 to FLAC in seconds
Every MP3 to FLAC conversion runs on our servers, so your device stays fast and the output quality stays intact.
Fast, cloud-powered
No queue, no waiting. Files are processed on high-performance servers and returned in seconds, even for large files.
Secure & private
Encrypted in transit and never shared with anyone. Uploads are erased the moment your job completes, and results shortly after.
Free - no account needed
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Developer API
Convert MP3 to FLAC via API
Automate MP3 to FLAC conversions in three steps: create a job, upload your file, then poll for the result.
# 1. Create job
curl -X POST https://api.runconvert.com/v3/jobs \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"tag": "mp3-to-flac",
"tasks": {
"upload-file": {
"operation": "import/upload"
},
"convert": {
"operation": "convert",
"input": "upload-file",
"output_format": "flac"
},
"export-result": {
"operation": "export/url",
"input": "convert"
}
}
}'
# 2. Upload your file (use upload_url from the response)
curl -X PUT "$UPLOAD_URL" --upload-file input.mp3
# 3. Poll for result
curl https://api.runconvert.com/v3/jobs/$JOB_ID?include=tasks \
-H "Authorization: Bearer YOUR_API_KEY"Replace YOUR_API_KEY with your RunConvert API key. Get your free API key at runconvert.com/api.