> ## Documentation Index > Fetch the complete documentation index at: https://www.helius.dev/docs/llms.txt > Use this file to discover all available pages before exploring further. # Get IDL > Get the IDL that was in effect for a Solana program at any slot, from the catalog Parsed Events uses to decode instructions. The path parameters, response schema, and examples on this page are generated from the OpenAPI definition. Get IDL returns a program's IDL as of a slot: the latest version that became active at or before `slot`. `slot` doesn't need to match a version exactly, so you can pass any point in history. To fetch one specific version, pass its `slot` from [List IDL Versions](https://www.helius.dev/docs/api-reference/parsed-events/idl-versions.md). The IDL comes from the same catalog that Parsed Events and [Parsed Streams](https://www.helius.dev/docs/parsed-streams.md) use to decode instructions. The [Orb explorer](https://www.helius.dev/docs/orb/explore-programs.md) uses these endpoints to show program IDLs. ## Use Cases * **Decode history with the right interface.** Pass a transaction's slot to get the IDL that was live when it executed. Programs change their instructions and accounts over time, so the current IDL can misread older transactions. * **Find exact names for filters.** [Scan Transaction History](https://www.helius.dev/docs/api-reference/parsed-events/scan.md) `match.programs[].instructions` accepts instruction names as the IDL spells them. * **Review interface changes.** Fetch two versions and compare their `instructions` to see what an upgrade added or removed. See the example on [List IDL Versions](https://www.helius.dev/docs/api-reference/parsed-events/idl-versions.md#example-detect-a-new-idl-version). ## IDL Formats The response is the IDL document as stored. Programs in the catalog use one of two Anchor formats, and one program's versions can use both. Check which format you received before reading it: | | Legacy Anchor (before 0.30) | Anchor 0.30+ | | - | - | - | | Program name and version | Top-level `name` and `version` | `metadata.name` and `metadata.version` | | Program address | No top-level `address` | Top-level `address` | | Instruction discriminator | Not included | `instructions[].discriminator` | | Instruction account flags | `isMut`, `isSigner` | `writable`, `signer` | Both formats have `instructions`. Most IDLs also have `accounts`, `types`, and `errors`, and many have `events`. ## Credits Each request costs **10 credits** and is available on all plans. See [Credits](https://www.helius.dev/docs/billing/credits.md#parsed-events). ## Errors | Status | When | | - | - | | `400` | `programId` isn't a valid base58 address, or `slot` isn't an unsigned 64-bit integer. | | `401` | The API key is missing or invalid. The body is plain text: `Unauthorized`. | | `404` | The catalog has no IDL for the program, or no version was active at or before `slot`. | Other errors return a JSON body with an `error` message, such as `{"error": "no IDL found for program KLend2g3cP87fffoy8q1mQqGKjrxjC8boSyAYavgmjD at or before slot 1"}`. ## Request Parameters **programId** `string` *required* Program address, base58-encoded. **slot** `number` *required* Slot to look up. It doesn't need to match a version's activation slot. Pass a `slot` from List IDL Versions to get that exact version, or a transaction's slot to get the IDL in effect when it executed. ## OpenAPI ````yaml openapi/parsed-events.yaml GET /v1/parsed-events/idl/{programId}/{slot} openapi: 3.0.3 info: title: Parsed Events version: 0.1.0 description: Parse Solana transactions and parsed transaction history with Parsed Events. servers: - url: https://mainnet.helius-rpc.com security: - ApiKeyQuery: [] paths: /v1/parsed-events/idl/{programId}/{slot}: get: tags: - Parsed Events summary: Get IDL description: >- Get the IDL that was in effect for a program at a slot, which is the latest version activated at or before `slot`. operationId: getIdlParsedEvents parameters: - $ref: '#/components/parameters/ProgramId' - name: slot in: path required: true description: >- Slot to look up. It doesn't need to match a version's activation slot. Pass a `slot` from List IDL Versions to get that exact version, or a transaction's slot to get the IDL in effect when it executed. schema: type: integer format: uint64 minimum: 0 example: 205509752 responses: '200': description: >- The IDL document as stored. Both the legacy Anchor format and the Anchor 0.30+ format occur, so check which one you received before reading it. content: application/json: schema: $ref: '#/components/schemas/Idl' examples: Legacy Anchor IDL: summary: >- Kamino Lend at slot 182747476 (trimmed to one instruction and one error) value: name: kamino_lending version: 0.1.0 instructions: - name: refreshObligation accounts: - name: lendingMarket isMut: false isSigner: false - name: obligation isMut: true isSigner: false args: [] errors: - code: 6000 name: InvalidMarketAuthority msg: Market authority is invalid Anchor 0.30+ IDL: summary: >- Pump AMM at slot 454326107 (trimmed to one instruction and one error) value: address: pAMMBay6oceH9fJKBRHGP5D4bD4sWpmSwMn52FMfXEA metadata: name: pump_amm version: 0.1.0 spec: 0.1.0 description: Created with Anchor instructions: - name: toggle_boost discriminator: - 117 - 161 - 160 - 74 - 223 - 137 - 118 - 99 accounts: - name: admin signer: true relations: - global_config - name: global_config writable: true args: - name: enabled type: bool errors: - code: 6000 name: FeeBasisPointsExceedsMaximum '400': $ref: '#/components/responses/IdlBadRequest' '401': $ref: '#/components/responses/Unauthorized' '404': description: >- The catalog has no IDL for the program, or no version was active at or before `slot`. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: default: value: error: >- no IDL found for program KLend2g3cP87fffoy8q1mQqGKjrxjC8boSyAYavgmjD at or before slot 1 components: parameters: ProgramId: name: programId in: path required: true description: Program address, base58-encoded. schema: type: string example: KLend2g3cP87fffoy8q1mQqGKjrxjC8boSyAYavgmjD schemas: Idl: type: object additionalProperties: true description: >- An IDL document, returned as stored. Two formats occur: - **Legacy Anchor** (before 0.30): top-level `name` and `version`. Instruction accounts use `isMut` and `isSigner`. - **Anchor 0.30+**: top-level `address` and `metadata` (`name`, `version`, `spec`, `description`). Instructions carry a `discriminator`, and instruction accounts use `writable` and `signer`. Both formats have `instructions`. Most IDLs also have `accounts`, `types`, and `errors`, and many have `events`. One program's versions can use different formats. ErrorResponse: type: object description: Request-level error response. properties: error: type: string description: Error message. responses: IdlBadRequest: description: >- `programId` isn't a valid address, or `slot` isn't an unsigned 64-bit integer. content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: Invalid program ID: value: error: 'invalid program id: notanaddress: String is the wrong size' Invalid slot: value: error: 'invalid activation slot: abc: invalid digit found in string' Unauthorized: description: The API key is missing or invalid. The body is plain text. content: text/plain: schema: type: string examples: default: value: Unauthorized securitySchemes: ApiKeyQuery: type: apiKey in: query name: api-key ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.