What audio format do Apple Podcasts and Spotify require?

Both Apple Podcasts and Spotify accept MP3 and AAC (M4A). MP3 at 128 kbps mono CBR is the safest universal choice because it works without conversion on every podcast app, RSS aggregator, and listener device. AAC at 96-128 kbps produces slightly better listener-side quality for the same bitrate, but MP3 has zero compatibility friction. Apple normalizes playback to -16 LUFS integrated, Spotify to -14 LUFS — both are within a small enough window that mastering to -16 LUFS works for both. Apple's per-episode size limit is 600 MB; Spotify's is 500 MB.

Should I upload MP3 or WAV to my podcast host?

Most hosts accept WAV but transcode it to MP3 for delivery anyway, so uploading WAV mainly matters when the host promises a high-quality re-encode (Buzzsprout's 192 kbps option, Transistor's high-bitrate plans). For a typical voice show, exporting 128 kbps mono CBR MP3 from your DAW gives the host nothing to re-encode and saves bandwidth on every upload. Upload WAV only if your host explicitly preserves it or if their re-encode produces noticeably better results than your DAW's MP3 export.

Does Pocket Casts or Overcast change my audio?

No. Pocket Casts, Overcast, Castro, and Castbox play the audio from your RSS feed without re-encoding. They apply playback-time DSP for features like Smart Speed (silence trimming) and Voice Boost (compression and loudness leveling), but those run on the listener's device and do not modify the source file. The audio quality in those apps is determined entirely by what your podcast host serves from the RSS enclosure URL.

What loudness target should I master a podcast to?

Master to -16 LUFS integrated with a -1 dBTP true peak ceiling, following AES TD1004.1 podcast loudness recommendations. Apple targets -16 LUFS playback normalization, Spotify -14 LUFS, Amazon Music and Google's podcast delivery -14 LUFS. Mastering to -16 LUFS hits Apple exactly and Spotify will turn the file up by 2 dB. Going louder than -14 LUFS means Spotify will turn the show down anyway, so the loudness war does nothing useful and costs you dynamic range.

Can I use Opus or FLAC for podcasts?

No, not as the delivery format. Opus is technically excellent — better than MP3 at every bitrate — but Apple Podcasts, Pocket Casts, and many older listener apps do not decode Opus from RSS feeds reliably. FLAC is lossless but RSS-distributed podcasts assume lossy delivery and few apps support FLAC playback over a podcast RSS enclosure. Use Opus or FLAC for archival and for direct platform delivery (Spotify Megaphone supports higher-quality internal codecs), but ship MP3 or AAC for the public RSS feed.

Audio Formats for Podcast Apps: Spotify, Apple, and More

Podcast platforms each have specific technical requirements for the audio they accept and the audio they deliver to listeners. The two are not the same — what you upload is rarely what listeners hear, because every major host re-encodes incoming audio to a streaming-optimized format. Understanding this gap is the difference between a podcast that sounds clean across every app and one that arrives at listeners with avoidable artifacts.

The Universal Source-of-Truth: MP3 at 128 kbps Mono

Every major podcast hosting platform — Buzzsprout, Libsyn, Anchor (now Spotify for Podcasters), Transistor, Captivate, RSS.com, Simplecast, Podbean — accepts MP3. MP3 is the safest delivery format because it travels through every host, every RSS aggregator, and every listener app without special handling.

Recommended source MP3 specs for cross-platform delivery:

Bitrate: 128 kbps CBR for voice-only content. 192 kbps for shows with music beds or produced segments.
Channels: Mono for solo and interview shows. Stereo for narrative documentaries or shows with stereo sound design.
Sample rate: 44.1 kHz. Some pro workflows use 48 kHz; both are accepted by every host.
Encoder mode: CBR (constant bitrate). Some apps mishandle VBR MP3 duration display and seeking.
Loudness: -16 LUFS integrated, -1 dBTP true peak, following EBU R128 / AES TD1004.1 podcast loudness recommendations.

A one-hour show at 128 kbps mono is approximately 56 MB — manageable for any hosting plan and quick to download for listeners on cellular.

What Apple Podcasts Accepts and Re-encodes To

Apple Podcasts accepts MP3 and M4A (AAC) up to 600 MB per episode. There is no documented duration cap, but episodes over 4 hours sometimes break. Apple normalizes playback to -16 LUFS, which means a podcast mastered to -20 LUFS will be quietly boosted in the app and a podcast mastered to -10 LUFS will be turned down — your absolute peak does not matter, your integrated loudness does.

Apple delivers most episodes to listeners as AAC at 64-128 kbps depending on the source bitrate and connection. Voice-heavy content at AAC 64 kbps sounds substantially better than MP3 at the same rate because AAC is roughly 30% more efficient per bit. The takeaway: even if you upload MP3, Apple is transcoding for delivery — your source quality matters because it sets the ceiling, not the floor.

Required metadata: title, artist, and album art embedded as ID3 tags (for MP3) or iTunes-format tags (for M4A). Artwork must be square JPG or PNG between 1400x1400 and 3000x3000 pixels, sRGB color space, under 500 KB.

Spotify Podcasts Specs

Spotify accepts MP3 and AAC. File size limit: 500 MB per episode. Spotify's normalization target is -14 LUFS — slightly louder than Apple's -16 LUFS, but the difference is small enough that mastering to -16 LUFS integrated works on both platforms with minimal impact. Spotify's player decodes Ogg Vorbis at 96-256 kbps (depending on listener tier) for most podcast playback, transcoded server-side from your source upload. Free users hear lower-bitrate streams; Premium subscribers get higher quality.

For shows distributed exclusively through Spotify (Megaphone, Anchor), Spotify can use the original audio for direct playback inside the Spotify app, bypassing the Ogg Vorbis transcode in some cases.

Google Podcasts, YouTube Music, and Amazon Music

Google Podcasts (deprecated 2024) handed listeners off to YouTube Music, which accepts the standard podcast formats and transcodes incoming audio to AAC for delivery. Amazon Music's podcast offering accepts MP3 and AAC, normalizes to -14 LUFS like Spotify, and delivers primarily AAC at 96-256 kbps. iHeartRadio accepts MP3 and AAC up to 250 MB per episode.

Hosts and What They Re-encode Incoming Audio To

Most hosts re-encode for at least one of: CDN delivery efficiency, mobile data savings, or RSS feed standardization.

Buzzsprout keeps original audio if MP3, transcodes others to MP3 at the source bitrate. Their Magic Mastering feature applies loudness normalization, EQ, and noise reduction before delivery.
Libsyn stores the original; some plans support 'Smart' MP3 optimization that shrinks files for mobile delivery.
Anchor / Spotify for Podcasters transcodes everything to a consistent MP3 internal format and serves Ogg Vorbis to Spotify clients.
Transistor keeps the source MP3, recommends 96-128 kbps mono for voice.
Captivate and Podbean keep original where compatible, transcode otherwise.

Knowing your host re-encodes is exactly why uploading a clean MP3 from your DAW beats letting the host transcode from a lossy intermediate. Upload at 128 kbps mono CBR so the host has minimal reason to touch it.

Pocket Casts, Overcast, Castbox, Castro

These player apps consume the RSS feed your host generates. They play whatever audio the feed points to without further re-encoding (with exceptions for chapter and silence-trimming features that re-render locally). The audio quality your listeners hear in these apps is set by the audio in your feed, not by the app.

Overcast is notable for processing inbound audio through its 'Smart Speed' (silence shortening) and 'Voice Boost' (loudness leveling) features client-side. These do not re-encode the source — they apply DSP at playback time.

RSS Feed Enclosure Types

The RSS feed's '' tag declares each episode's MIME type. Get this wrong and apps may refuse to play the file:

MP3: 'audio/mpeg'
AAC in M4A: 'audio/x-m4a' (Apple), 'audio/mp4' (broadly compatible)
AAC in MPEG-4 audio: 'audio/aac' (less commonly accepted)

Most hosts handle this automatically. If you self-host, double-check the MIME type in your generated feed — Pocket Casts and Overcast are particularly strict.

Recommended Source Format and Workflow

Record in 48 kHz 24-bit WAV inside your DAW. Edit, denoise, and level in WAV. Master to -16 LUFS / -1 dBTP. Export final delivery as 128 kbps mono CBR MP3 (192 kbps stereo if music). Upload that MP3 to your host. This produces the best listener-side quality across Apple, Spotify, and every other major platform without giving the host any reason to re-encode.

For more on the WAV vs MP3 source decision, see MP3 vs WAV for podcasting. For the bitrate ladder details, see audio bitrate explained. For the broader format picker, see best format for podcasts and the audio normalization primer. When a single recording captures multiple episodes back-to-back, split the audio into separate episode files before uploading — most hosts charge per file, not per minute, so each split keeps its own publish date and slot in the feed.