---
updatedAt: 2025-12-08T06:11:46.000Z
agentTools:
projectIndex: https://docs.blockvision.org/llms.txt
---
# Smart Contract Verification on Monad Explorer
When you deploy a smart contract on the Monad network, it’s best practice to **verify and publish** your source code so others can inspect and interact with it transparently.
This guide describes **three verification methods**:
1. **Via Explorer UI**
2. **Via Foundry CLI**
3. **Via Hardhat Plugin**
***
## 🔗 Sourcify API Endpoint
All verification methods ultimately interact with BlockVision's **Sourcify** verification service. **Both mainnet and testnet use the same Sourficy URL.** The network will be detected automatically based on the RPC.
**SOURCIFY API URL:**
```
https://sourcify-api-monad.blockvision.org/
```
> For the verifier URL, please make sure to use
>
> — including '/' at the end of url
>
> — instead of
## 🖥️ 1. Verify via Explorer UI
The simplest way to verify your contract is through the **Monad Explorer** website.
### Steps
1. Visit the verification page: Mainnet and Testnet
2. Select the correct **network** (Mainnet or Testnet).
3. Enter your **contract address**.
4. Upload or paste your:
* `metadata.json` (compiler metadata)
* Contract source file(s) or flattened source
5. Click **“Verify”**. The explorer will match the uploaded bytecode against the on-chain deployed contract.
6. Once successful, your contract will display as **“Verified”** in the explorer.
7. You can then view the verified source code, ABI, and other details on the contract’s page.
### Tip: If verification fails, check compiler version, optimization settings, and metadata consistency.
***
## 🛠️ 2. Verify via Foundry
If you use **Foundry** for development, you can verify directly through the CLI.
### 📘 Example Repository
For a complete self-check example, you can use this repository:\
👉
This sample project demonstrates:
* Deploying a simple Solidity contract using Foundry
* Verifying it on the Monad
* Testing the Sourcify verification pipeline end-to-end
### Prerequisites
* Foundry installed (`forge`)
* Properly configured `foundry.toml`
Example configuration:
````toml
[profile.default]
src = "src"
out = "out"
libs = ["lib"]
metadata = true
metadata_hash = "none"
use_literal_content = true
# Verification Command
```bash
forge verify-contract \
--rpc-url https://rpc.monad.xyz \
--verifier sourcify \
--verifier-url 'https://sourcify-api-monad.blockvision.org/' \
--chainid 143 \
\
[contractFile]:[contractName]
````
**Example:**
```bash
forge verify-contract \
--rpc-url https://rpc.monad.xyz \
--verifier sourcify \
--verifier-url 'https://sourcify-api-monad.blockvision.org/' \
--chainid 143 \
0xBA01C22bf93984B79fda58144abc384afb9bC1fd \
src/Counter.sol:Counter
```
### Troubleshooting API Deserialization Errors
#### When running contract verification commands, if you encounter this error:
```javascript
ERROR etherscan: Failed to deserialize response: expected value at line 1 column 1
ERROR etherscan: Failed to deserialize ABI response err=Serde { error: Error("expected value", line: 1, column: 1)
Error: Provided URL https://sourcify-api-monad.blockvision.org/ is host only. Did you mean to use the API endpoint `https://sourcify-api-monad.blockvision.org//api` ?
```
#### Solution 1: Double Check Verifier URL
Make sure your --verifier-url is `https://sourcify-api-monad.blockvision.org/` (with trailing slash), not `https://sourcify-api-monad.blockvision.org` (without trailing slash)
#### Solution 2: Remove Etherscan API Key Configuration
**Step 1: Check Your Configuration**
Run the following command to view your current Foundry configuration:
```javascript
forge config
```
**Step 2: Locate the Problem**
Look through the output for any etherscan\_api\_key entries. The configuration might appear in different sections depending on your setup.
**Step 3: Remove the Conflicting Configuration**
If you find `etherscan_api_key` in your configuration, remove it from your foundry.toml file. The configuration file is typically located in your project root directory.
**Step 4: Confirm Configuration Change**
Run forge config again to confirm that etherscan\_api\_key has been successfully removed:
```
forge config
```
Check the output to ensure there are no etherscan\_api\_key entries remaining in your configuration.
**Step 5: Retry Contract Verification**
### Notes
* Ensure the compiler version and optimization flags are identical to those used during deployment.
* On success, your contract will automatically appear as **verified** on Monad Explorer.
* If verification fails, inspect your metadata or recompile with the same settings.
***
## ⚙️ 3. Verify via Hardhat
For projects built with **Hardhat**, you can enable Sourcify-based verification with minimal setup.
### 1. Install the verification plugin
```bash
npm install --save-dev @nomicfoundation/hardhat-verify
```
### 2. Configure your `hardhat.config.js`
```js
require("@nomicfoundation/hardhat-verify");
module.exports = {
networks: {
monad: {
chainId: 143,
url: "https://rpc.monad.xyz"
},
},
etherscan: {
enabled: false
},
sourcify: {
enabled: true,
apiUrl: "https://sourcify-api-monad.blockvision.org/"
},
solidity: {
version: "0.8.x",
settings: {
optimizer: {
enabled: true,
runs: 200
}
}
}
};
```
### 3. Run the verification command
```bash
npx hardhat verify --network monad --contract [contractFile]:[contractName] \
[...constructorArgs]
```
**Example:**
```bash
npx hardhat verify -- network monad \
--contract src/Counter.sol:Counter \
0x60511f775dD4287a78d338a0727DF49363db5B33
```
Hardhat will automatically submit your compiled metadata and sources to the Sourcify API and display the verification status.
## 🧩 Troubleshooting
* **Bytecode mismatch** → Confirm same compiler version & optimization settings.
* **Metadata errors** → Ensure `metadata.json` matches deployed build.
* **Multiple files** → Use flattened source or include full project folder for Sourcify.
* **Network errors** → Verify the correct RPC URL and chain ID.