Pure proxy address

A pure proxy is a keyless account created by Proxy.create_pure. Its address depends on who created it, the proxy type, an index, and exactly where the creating extrinsic landed on chain.

Loading the chain's runtime metadata…

Spawner

The account that called create_pure. Any SS58 prefix or 0x public key.

Proxy type

Index

create_pure's index argument, usually 0.

Block height

Of the create_pure extrinsic. Paste an extrinsic id like 9305288-10 to fill both.

Extrinsic index

Its position in that block.

The proxy type is the variant's index in the runtime's ProxyType list (Any is 0).

How the address is derived

The Proxy pallet hashes the text modlpy/proxy____, the spawner's account, the block height, the extrinsic's index in that block, the proxy type and the index with BLAKE2b-256. The hash is the pure proxy's account id.

The proxy type is encoded as its position in the runtime's ProxyType list, which this page reads from the chain's metadata.
The index tells apart pure proxies created by the same account in the same extrinsic, such as several in one batch. It is usually 0.
The block height and extrinsic index are part of the hash, so the address can only be known once the extrinsic is included.

Why you might need it

To remove a pure proxy with kill_pure, the chain needs the same height, extrinsic index, proxy type and index. If the address here matches your pure proxy, those are the values to use. The PureCreated event of the creating extrinsic shows the address the chain assigned.