UniCrypt

Developers that are listing their tokens on Decentralised Exchanges are granted LP tokens when they initiate a pool. These LP tokens, once in their possession, can be transferred like any other tokens on the blockchain they have been minted on (theoretically, LP tokens could also transit on other blockchains using bridges, but this is not something done very often)

A liquidity locker allows the developer to store these LP tokens in a smart contract, revoking his permission to move these LP from a start date (or, more accurately, a start block) to an end date (end block).

The Unicrypt liquidity locking service is widely used when it comes to DeFi projects. We could even argue that it is an industry standard that comes right after the creation of any new liquidity pool on different Decentralised exchanges.