> ## Documentation Index
> Fetch the complete documentation index at: https://docs.primev.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Why Should Validators Opt In to Fast Protocol?

> Understanding why opting in to Fast Protocol is rational and profitable for validators.

Fast Protocol is designed so that **opting in is rational and strictly profitable** for validators. This page explains the incentive model and what validators gain.

## What Opted-In Validators Earn

| Validator Type   | Approx. mev Capture   | Reason                      |
| ---------------- | --------------------- | --------------------------- |
| **Opted-In**     | \~95% of FAST RPC mev | Full backrun mev + residual |
| **Not Opted-In** | \~5% of FAST RPC mev  | Similar to mev Blocker      |

Opted-in validators enjoy approximately **20x higher mev capture** on FAST RPC flows compared to non-opted-in validators.

## Where the Value Comes From

Opted-in validators gain from three sources:

1. **Backrun-captured mev** from FAST RPC bundles routed to their blocks
2. **Their share of traditional builder-to-validator mev** (unaffected by opting in)
3. **Competitive advantage** in attracting order flow — searchers and builders prefer blocks where their bundles will be honored

## When Is Opting In Profitable?

Opting in is designed to be strictly profitable for validators. In future protocol versions, opted-in validators may pay a dynamic fee taken from the producer reward of their opt-in blocks. This fee is bounded so that it never exceeds the additional value an opted-in validator receives from mev-commit — opting in remains net-positive by design.

No fee is taken today.

## How to Opt In

Validators can opt in through the mev-commit protocol. See the [Validator Guide](/v1.2.x/get-started/validators/validator-guide) for setup instructions, or register via [EigenLayer](/v1.2.x/get-started/validators/eigenlayer) or [Symbiotic](/v1.2.x/get-started/validators/symbiotic) for restaking-based opt-in.