Overview
Metadata Registry Testnet is a public directory that lets token developers give their test tokens a readable name, ticker, and logo. On the blockchain, a token is known only by a long code made of letters and numbers. This registry works like a phone's contact list: the network keeps the number, and the registry supplies the name that wallets, explorers, and apps can display instead1.
The registry follows CIP-26, a Cardano Improvement Proposal (a formal design document for the network) that defines how details stored off the blockchain map to on-chain IDs2. It covers Cardano's public testnets, practice networks such as preprod and preview that use test ADA, which has no value3. Tokens on the main network belong in the separate Cardano Token Registry instead1.
The Cardano Foundation maintains the Metadata Registry Testnet repository on GitHub1. The offchain-metadata-tools used to create and validate entries come from Input Output4.
Key Features
- Readable names for test tokens. Each entry links a token's on-chain ID (its policy ID, a code derived from the token's minting rules, plus its asset name) to a required name and description, with an optional ticker, website link, PNG logo, and number of decimal places1.
- Changes are reviewed before they count. New entries and edits arrive as GitHub pull requests, which are proposed changes to the repository. Each one must pass automated format checks and a human review before it is merged1.
- Proof of who controls a token. An entry can include the token's minting policy, the rules for who can create it, so apps can confirm the submitter controls the token. Without it, as with Plutus smart-contract tokens, the wallet or app reading the entry relies on signatures from keys its user trusts1.
- One lookup service across testnets. Apps read entries through a public API (a connection point other software can call) at preprod.tokens.cardano.org, which also serves preview entries despite its name1.
- Test before going live. The Cardano Foundation runs the lookup service for both mainnet and the preprod testnet through the same interface, so developers can check how their token details resolve before launch5.
What to Expect
The Metadata Registry Testnet is a GitHub repository, not an app with a sign-up screen. Token creators prepare one small JSON file (a plain text data file) describing their token; the token-metadata-creator in offchain-metadata-tools helps build and validate it4. The file is named after the token's ID in lowercase, added in a single commit (one saved set of changes), and submitted as a pull request with no other files. Each entry can be up to 370 KB, and the README (the repository's front-page instructions) points to a step-by-step wiki for first-timers1.
Developers building wallets or block explorers can read entries through the API instead of the repository. The Cardano Foundation's service combines entries from this registry with CIP-68 token details, which are stored on the blockchain itself. By default it prefers the on-chain value and falls back to the registry field by field when one is missing5. The preprod service publishes its full API documentation online6.
Everyday users rarely visit the Metadata Registry Testnet directly. They see its effect when a testnet wallet shows a token's name and logo rather than a raw code, which is the problem CIP-26 was written to solve2. The repository's tooling and documentation are open source under the Apache 2.0 license, while the entries themselves are submissions from token creators, provided as-is1. It sits alongside other registries that attach readable information to on-chain data.
