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AAC to FLAC Converter

Convert AAC to FLAC online for free. Fast, secure, and high-quality conversion with no sign-up or software required.

  • Free to use
  • No file stored beyond 1 hour
  • Encrypted over TLS 1.2/1.3
  • No watermarks

Drag and drop your files here or click to upload.

Maximum file size is 1GB

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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.

  1. 01

    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.

  2. 02

    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.

  3. 03

    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.

AAC to FLAC

Why convert AAC to FLAC?

AAC is a lossy format, while FLAC is a lossless format.

  • No further quality loss

    FLAC is lossless, so from here on the file keeps every detail - good for editing and archiving.

  • Where FLAC works best

    Archiving music at full CD quality in about half the size of WAV.

AAC vs FLAC: what's the difference?

PropertyAACFLAC
TypeAudioAudio
CompressionLossy (smaller files, some quality loss)Lossless (no quality loss)
Opens inApple devices, Android and most media playersMost music players and Android; iPhone via the Files app or VLC
Best forBetter quality than MP3 at the same file sizeArchiving music at full CD quality in about half the size of WAV

What is an AAC file?

Advanced Audio Coding

Developed By
Bell Labs, Fraunhofer IIS, Dolby, Sony, Nokia
Initial Release
1997
MIME Type
audio/aac

Advanced Audio Coding (AAC) is a lossy digital audio compression standard defined by ISO/IEC 13818-7 (MPEG-2) and ISO/IEC 14496-3 (MPEG-4). Developed by a consortium including Bell Labs, Fraunhofer IIS, and Dolby Laboratories as the successor to MP3, AAC utilizes the Modified Discrete Cosine Transform (MDCT) algorithm and perceptual noise shaping to discard imperceptible signal components. It supports up to 48 audio channels, arbitrary sample rates, and utilizes extensions such as Spectral Band Replication (SBR) to achieve higher fidelity at lower bitrates than predecessor formats.

How to open an AAC file

AAC serves as the default audio container for Apple's iTunes and iOS devices, ensuring native support within the macOS Core Audio framework and Apple Music. Windows 10 and 11 provide native decoding support via the Groove Music and Windows Media Player applications. For cross-platform playback or advanced stream analysis, users should utilize VLC Media Player or FFmpeg, which contain the necessary libavcodec libraries to decode AAC streams without external codec packs.

What is a FLAC file?

Free Lossless Audio Codec

Developed By
Josh Coalson / Xiph.Org Foundation
Initial Release
2001
MIME Type
audio/flac

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.

More tools

More free audio tools

All audio conversions

Why RunConvert

The fastest way to convert any file

Purpose-built for speed, privacy, and breadth of format support.

  • Convert AAC to FLAC in seconds

    Every AAC 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

    Convert without creating an account - no credit card, no trial clock. Sign in only if you want history and higher daily limits.

Developer API

Convert AAC to FLAC via API

Automate AAC to FLAC conversions in three steps: create a job, upload your file, then poll for the result.

Replace YOUR_API_KEY with your RunConvert API key. Get your free API key at runconvert.com/api.

# 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": "aac-to-flac",
    "tasks": {
      "upload-file": {
        "operation": "import/direct/upload"
      },
      "convert": {
        "operation": "convert",
        "input": "upload-file",
        "input_format": "aac",
        "output_format": "flac"
      },
      "export-result": {
        "operation": "export/url",
        "input": "convert"
      }
    }
  }'

# 2. Upload your file (upload_url of the upload-file task in the response)
curl -X PUT "$UPLOAD_URL&filename=input.aac" --upload-file input.aac

# 3. Poll for result
curl https://api.runconvert.com/v3/jobs/$JOB_ID?include=tasks \
  -H "Authorization: Bearer YOUR_API_KEY"

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