extrL

Download a Solana program's on-chain Anchor IDL straight from the chain - no anchor toolchain, no RPC SDK, single static binary.

Anchor programs (pre-1.0) publish their IDL to a deterministic account derived from the program id and the seed anchor:idl. extrL derives that address, fetches the account over plain JSON-RPC, strips the header, zlib-inflates the payload, and writes the IDL JSON.

Install

cargo install extrL
# or
cargo build --release   # -> target/release/extrL

Requires a current Rust toolchain (some transitive deps use edition 2024).

Usage

extrL <PROGRAM_ID>                          # writes <idl name>.json
extrL <PROGRAM_ID> -o jup.json              # custom output path
extrL <PROGRAM_ID> -s                       # print to stdout
extrL <PROGRAM_ID> -u https://api.devnet.solana.com
extrL --completions bash > extrL.bash       # shell completions

flag	meaning	default
-u, --url	RPC endpoint	https://api.mainnet-beta.solana.com
-o, --out	output file (conflicts with -s)	<idl name>.json, else <PROGRAM_ID>.json
-s, --stdout	print instead of writing a file	off
--completions <SHELL>	print shell completions and exit	—

The output file defaults to the IDL's own name (e.g. jupiter.json), falling back to the program id when the IDL has no name.

Programs without a published on-chain IDL produce a clear error rather than an empty file. Requests use a 10s connect / 30s read timeout and retry transient 429/5xx responses with backoff — a rate-limited public RPC reports a clear hint to pass your own -u endpoint.

How it works

base    = find_program_address([], program_id).0
idl_acc = create_with_seed(base, "anchor:idl", program_id)

account layout:
  [0..8]            8-byte account discriminator
  [8..40]           authority (Pubkey)
  [40..44]          data_len  (u32 LE)
  [44..44+data_len] zlib-compressed IDL JSON

Derivation is implemented directly with sha2 + curve25519-dalek (the ed25519 on-curve check) and cross-checked byte-for-byte against solders. No solana-sdk dependency.

Notes

• Targets the legacy anchor:idl account, which virtually every deployed Anchor program uses.
• Anchor 1.0 began migrating IDL storage to a separate Program Metadata standard. Programs that only publish via Program Metadata are not covered yet - a future --source metadata path can be added.

License

MIT