What Are Rollups? ZK Rollups and Optimistic Rollups | Explained

Scalability is one of the major issues of layer 1 Ethereum, layer 2 was established to resolve scalability issues, and rollups (ZK Rollups and Optimistic Rollups) are the latest projects of layer 2 Ethereum. In layer 1 all the transactions are done one by one which is time-consuming and complex whereas layer 2 sends the batch of transactions which is ultimately efficient and less costly than layer 1.

Today’s article is all about layer-2 Ethereum so let’s get started and know more about layer-2 Ethereum-based blockchain!

What Are Rollups?

Rollups are the layer 2 Ethereum-based blockchain that processes a bunch of transactions at a time and then turns them into a single unit. Furthermore, it sends multiple transactions as a single unit instead of sending each transaction separately. This approach helps to reduce the gas fee and time consumption.

Let’s understand this with a real-time example, for instance, you are running a business food supply, and one of your clients demands a specific quantity of food. Here by using the rollups concepts you will send the whole quantity at once from the data warehouse to the client’s destination instead of sending one item at a time. But if you send item by item then it would be quite time-consuming, less-efficient as well as costly.

Once the transaction is successfully done by the rollups, the batch of transactions would be transmitted to the layer 1 Ethereum blockchain for settlement. So here; one thing is clear: all the execution of transactions would be done on layer 2 and the settlement would be done on layer 1.

Rollup have two major types:

  1. Optimistic Rollups
  2. ZK Rollups

What Are Optimistic Rollups?

As it is represented by a name that would be optimistic in functionality. Optimistic Rollups assume all the transactions are valid by default and send them without validity proof as well as it takes more withdrawal time.

In optimistic rollups, all the transactions would be sent at once without taking care of whether it is valid or invalid and then wait for the invalid transaction response/ request, after receiving an invalid request it would start working on it to make it valid.

It has two major projects:

  1. Optimism Network
  2. Arbitrum Network

What Are ZK Rollups?

ZK Rollups check each transaction firstly whether it is valid or invalid and send them with validity proof. Furthermore, it takes less withdrawal time. Furthermore, it is still under development and not matured yet, ZK Sync is one of the famous projects of ZK Rollups but it is still working on Testnet, and hasn’t deployed on Mainnet yet.


Rollups are the latest projects on Ethereum-based blockchain and vary in layer 2, scalability is one of the major drawbacks in layer-1 Ethereum-based blockchain. So, rollups come to resolve this issue. In layer 1 until the first transaction is not to be done, the second transaction would not be initiated as roll ups can send the batch of transactions at once.

About the author