What is Castr?

Castr.fm is an immutable podcast upload portal and aggregator for Bitcoin.

All podcasts uploaded via Castr are stored directly on the Bitcoin (BSV) blockchain and can be syndicated using any traditional podcatcher or index supporting RSS feeds (iTunes, Google Podcasts, Overcast, gPodder, etc).

By storing podcasts on the blockchain, audio data uploaded using Castr provides censorship-resistance and data persistence unmatched by conventional podcast hosting platforms.

We believe that your podcasts are your sole digital property, not the property of rent-seeking podcast hosts leasing your creativity back to you.

How Much Do Podcast Uploads Cost?

Unlike traditional podcast hosting services, Castr has no monthly subscription fees or costs.

Instead, we adopt a pay per upload model - you pay a one-time fee per podcast uploaded, regardless of how many downloads your podcast receives.

As podcasts uploaded using Castr are stored on-chain, a transaction fee paid directly to miners is required. Castr takes a transparent 10¢ per MB or a flat $3 per podcast cut, whichever is cheapest.

All other costs are collected by the Bitcoin miners themselves as transaction fees.

Can I Earn Money on Castr?


The value-for-value model is fully supported on Castr - audience members can Cheer your podcast to show direct financial support at the rate of 1¢ per cheer. All Comments on Castr cost 10¢ - 8¢ goes directly to the podcaster while Castr collects a 2¢ platform fee.

We plan to support other methods of monetizing your podcasts in the future.

What is the Upload Quality Selector?

At present, on-chain filestorage on the Bitcoin network is more expensive than traditional filehosting. While on-chain data storage fees are dropping all the time, we at Castr believe in making immutable podcasts as affordable as possible.

We also believe that a podcaster's job is to create engaging and quality content, not to fiddle endlessly with filesizes to ensure an affordable upload price.

This is why we have implemented a quality selector in our upload portal.

Depending on your selection, we'll resample your audio to lower its filesize, and ultimately, your on-chain storage costs. The lower the quality you select, the cheaper your file upload will be!

Castr will never resample your audio below a 22050Hz sample rate and a 16kbps bitrate respectively to ensure your podcast remains listenable.

Currently, we set our low quality audio compression target at 20MB and our high quality target at 50MB, but we plan on offering more granularity of compression control to podcasters in the near future.

What Data Does Castr Store On-Chain?

In addition to storing podcasts on-chain, Castr also saves the following data to the Bitcoin blockchain:

  • Comments left on your podcasts
  • Records of Cheers associated with your podcast

At present, Castr does not store the following data on-chain:

  • Album art
  • Show title
  • Show description
  • ID3 images

Large metadata payloads like images increase on-chain upload costs, but we may consider adding them in the future.

How Do I Contact Castr?

Have any questions not answered here? How about a feature request or bug report? We want to hear from you!