DEV Community: kilozz

Test JSON-RPC Calls Without Leaving Your Browser: The Playground Every Web3 Developer Needs

kilozz — Mon, 12 Oct 2026 14:59:36 +0000

Test JSON-RPC Calls Without Leaving Your Browser: The Playground Every Web3 Developer Needs

You're debugging a smart contract interaction. You need to test an eth_call. You need to check eth_getBalance for a specific address. You want to see what eth_getLogs returns for a particular event.

What do you do?

If you're like most developers, you open a terminal, fire up curl or a Python script, construct the JSON-RPC payload, hit the endpoint, parse the response, and repeat for every method you need to test. It works, but it's slow. And when you're in debugging mode, slow is the last thing you want.

The Friction of Traditional RPC Testing

JSON-RPC is the language blockchains speak. Every wallet, every dApp, every on-chain tool communicates through JSON-RPC calls. But testing these calls has always been unnecessarily cumbersome:

Terminal workflows require remembering method signatures, parameter formats, and endpoint URLs
No request history means you reconstruct the same calls every session
No presets for common methods means typing out {"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1} over and over
Endpoint switching means updating URLs manually when you want to test against a different chain

What a Modern RPC Playground Looks Like

Browser-Based, Server-Proxy Powered

Send JSON-RPC requests directly from your browser. The platform handles the proxying server-side, so you never deal with CORS errors. Pick a chain, pick a method, send the request, get the response. That's the entire workflow.

Method Presets for Common Calls

Stop typing boilerplate. Pre-built templates for the methods you use most:

eth_blockNumber — check current block
eth_getBalance — query any address balance
eth_call — execute read-only contract calls
eth_getTransactionByHash — look up transactions
eth_getLogs — filter event logs
And more

Select a preset, fill in the parameters, send. Done.

Request History, Saved Locally

Every request you make is saved in your browser. Come back tomorrow, last week's test is still there. No accounts, no cloud storage, just local persistence that works.

Export as cURL

Need to share a test case with a teammate? Export any request as a ready-to-run cURL command. One click, copy, paste into terminal.

Who Benefits

Smart contract developers testing contract interactions during development
dApp engineers debugging frontend-to-blockchain communication issues
Security researchers probing contract behavior with specific RPC calls
Anyone who's ever typed a JSON-RPC payload by hand and thought "there has to be a better way"

It's Free and Requires No Setup

No API keys. No sign-up. No configuration. Open the page, pick a chain, start testing. The server-side proxy handles all the complexity of routing your requests to the right endpoints.

Find it at https://rpchub.top/playground

Foundry's Cast in Your Browser: No Installation, No Setup, Just On-Chain Data

kilozz — Tue, 06 Oct 2026 01:23:47 +0000

Foundry's Cast in Your Browser: No Installation, No Setup, Just On-Chain Data

You need to check a wallet's token balance on a specific chain. You need to read a contract's storage slot. You need to look up the current block number or decode a transaction's input data.

If you have Foundry installed, you reach for cast. It's the Swiss Army knife of on-chain data queries. Fast, reliable, and familiar to anyone who's spent time in the Foundry ecosystem.

But what if you don't have Foundry installed? What if you're on a different machine? What if you just need to run one quick check and don't want to wait for foundryup?

The Problem with CLI-Only Tools

Command-line tools are powerful. They're also inconvenient when you need quick access from an unfamiliar environment. Installing Foundry takes time. Configuring it takes more time. And for simple read-only queries, it's overkill.

Even when you have it set up, switching between chains means updating RPC URLs, managing environment variables, and remembering the exact syntax for each command. It's not hard, but it's friction. And friction adds up.

Cast Terminal, Without the Setup

Web-Based Foundry Cast

A full Cast interface running in your browser. Type commands exactly as you would in a terminal. Get the same output format you're used to. The muscle memory transfers directly.

Read-Only Commands, Fully Supported

All the Cast commands you use for on-chain queries work here:

cast block-number — current block height
cast balance <address> — native token balance
cast call <contract> <signature> [args] — read contract state
cast code <address> — deployed bytecode
cast storage <address> <slot> — storage slot values
cast tx <hash> — transaction details
cast receipt <hash> — transaction receipt
And many more

Safety Built In

Dangerous commands like cast send and cast wallet are blocked. This is a read-only tool. You can query anything on-chain, but you can't accidentally send transactions or expose private keys.

Multi-Chain Support

Switch between chains without changing environment variables or updating config files. Pick your target network from a dropdown and run your commands. The platform routes everything through the appropriate RPC endpoint.

Who Uses This

Developers who need quick on-chain data checks without opening a terminal
Auditors reviewing contract state across multiple chains
Traders verifying balances or transaction details on the go
Anyone who uses Cast regularly but sometimes needs access from a machine without Foundry installed

Zero Installation

No curl | sh. No waiting for downloads. No configuration. Open the page, select a chain, start typing Cast commands. It's that simple.

Try it at rpchub.top/cast-playground

Stop Switching Chains! Check All Your Assets Across all Networks in 3 Seconds

kilozz — Fri, 02 Oct 2026 02:51:18 +0000

Check all Chains in 3 Seconds

Tired of switching between Ethereum, BSC, Polygon, Arbitrum, and a dozen other networks just to check your crypto balance?

You're not alone. Most crypto users have money scattered across multiple blockchains—but checking it all means opening countless tabs, typing your address over and over, and doing math to figure out what everything's worth in dollars.

It shouldn't be this hard.

The Problem: Your Assets Are Everywhere

Let's be honest. If you've been in crypto for more than a few months, you probably have:

Some ETH on Ethereum
BNB on BSC (maybe from trading fees)
MATIC or USDC on Polygon (from an NFT mint or DeFi transaction)
Tokens on Arbitrum or Base (from that airdrop you claimed)
And who knows what else on other chains you forgot about

Checking all of this manually? Easily 30 minutes of work. And you'll probably miss something anyway.

We Built the Solution You Need

RPC Hub lets you check your entire crypto portfolio across 13 major blockchains—in under 3 seconds.

Here's how simple it is:

Go to rpchub.top
Paste your wallet address (that long string starting with 0x...)
Hit enter
See everything—every coin, every chain, total value in USD

That's it. No wallet connection needed. No signing transactions. No installing browser extensions. Just paste and go.

What You'll See

All Major Chains Covered

We check your balances on:

Ethereum (ETH)
BNB Chain (BNB)
Polygon (MATIC)
Arbitrum
Optimism
Base
Avalanche (AVAX)
Plus 6 more popular networks

Native Coins + Stablecoins

You'll see:

Native tokens: ETH, BNB, MATIC, AVAX—whatever each chain uses
Stablecoins: USDT, USDC, DAI—the dollar-backed coins you can actually spend

Real Dollar Values

No more converting "0x56bc75e2d63100000" to "2.5 ETH" then looking up the price. We show you exactly how much everything is worth in US dollars right now.

Example result:

Ethereum:     2.5 ETH   = $4,625
BNB Chain:    10 BNB    = $3,100
Polygon:      5,000 USDC = $5,000
Arbitrum:     0.8 ETH   = $1,480
─────────────────────────────
Total:                   $14,205

Why This Matters

Find Forgotten Money

A user recently discovered $2,400 worth of tokens they forgot about on Arbitrum. A protocol had upgraded, changed its token contract, and their old tokens were just sitting there. They only found out because they used RPC Hub to check all their chains at once.

Another person found $800 in USDC stuck on Polygon from a failed bridge transaction months ago.

How much are you forgetting about?

Save Time Every Week

If you actively use multiple chains for DeFi, NFTs, or trading, you're probably wasting 2+ hours per week just checking balances. That's 100+ hours per year—time you could spend on actually making money, not counting it.

Make Better Decisions

Want to know if you have enough liquidity to jump into a new opportunity? Need to rebalance your portfolio? Planning taxes?

With RPC Hub, you get the full picture instantly. No guessing. No manual spreadsheets. Just accurate numbers when you need them.

Who Is This For?

✅ DeFi users with positions across multiple protocols and chains

✅ NFT collectors who've bought/sold on different marketplaces

✅ Traders moving funds between exchanges and wallets

✅ Anyone who's ever thought "I wonder what my total portfolio is worth right now"

Basically, if you have crypto on more than one blockchain, this tool was built for you.

It's Completely Free

✅ No account required (for basic queries)
✅ No wallet connection needed
✅ No hidden fees
✅ No data mining—we don't store your address or query history

We make money from premium features (like automated monitoring alerts), not from selling your data.

Security First

We never touch your assets. Period.

This tool is read-only. We simply look up public information that's already on the blockchain. We cannot:

Move your funds
Access your private keys
Sign any transactions
Do anything except show you your balance

Think of it like checking your bank balance online—you can see the number, but you can't move money without additional authentication.

How to Get Started (30 Seconds)

Step 1: Open rpchub.top in your browser

Step 2: Click on "Balance" or "Asset Query"

Step 3: Copy your wallet address from MetaMask (or any wallet) and paste it in

Step 4: Wait 2-3 seconds

Step 5: See your complete multi-chain portfolio

Total time: Less time than it took to read these instructions.

Real Stories From Real Users

"I thought my crypto journey was basically over—markets were down, I'd cashed most things out. Then I checked with this tool and found $3,200 scattered across chains I'd completely forgotten about. Best 3 seconds of my month."

— @crypto_recovering_degen

"Our team manages a treasury across 8 wallets on 6 different chains. This tool saved us from building a custom spreadsheet that would've taken days to create."

— @dao_treasurer_eth

"Found $800 USDC I didn't know I had. Enough said."

— @casual_nft_guy

Stop Guessing. Start Knowing.

Your assets are spread across multiple chains. That's just reality in 2024's crypto world.

The question is: Do you want to spend 30 minutes checking them one by one, or 3 seconds seeing everything at once?

Visit rpchub.top now. Paste your address. See your true net worth.

It really is that simple.

Free forever for basic queries. No signup required. Your data stays yours.

Stop Letting RPC Failures Kill Your DApp

kilozz — Mon, 28 Sep 2026 05:54:41 +0000

Stop Letting RPC Failures Kill Your DApp: Why Developers Across 500+ Chains Are Switching to This Monitoring Tool

It's 3 AM. Your DeFi protocol is down because an RPC node crashed, and you don't find out until users start complaining at 9 AM. Sound familiar?

In Web3, RPC nodes are your lifeline. Whether you're reading on-chain data, sending transactions, or listening to events, everything depends on RPC stability and response speed. But the reality is: public RPCs go down constantly, latency spikes without warning, blocks get stuck, and you're usually the last to know.

Today, let me introduce a RPC monitoring tool built specifically for Web3 developers — RPC Hub. Say goodbye to flying blind.

🔍 The Pain Point: Your Node Says "Online," But It's Actually Dead

Many developers rely on browser-based checks or Chainlist status pages, but these approaches have fatal flaws:

CORS limitations cause false positives: Many nodes are actually online, but browsers block them with CORS policies, showing "offline"
Connectivity only, no performance data: Being reachable doesn't mean it's usable. 50ms vs 5000ms latency is a world of difference
No historical data: When things break, you can't trace back to see if it's a one-off or a pattern
Zero alerting: You only find out nodes are down when users complain

💡 How RPC Monitor Solves These Problems

✅ Server-Side Probing, Zero CORS False Positives

RPC Hub uses server-side multi-node probing, sending requests directly from the server and completely bypassing browser CORS restrictions. This means:

100% accurate offline reports
No regional network limitations
Results that truly reflect node availability

✅ 7×24 Automated Monitoring, Instant Alerts on Anomalies

Just add the RPC endpoints you want to monitor, and the system automatically checks them at fixed intervals:

Online/offline status tracked in real-time
Response latency measured to the millisecond
Block height continuously verified (prevents "fake online" states where connection works but blocks are stuck)
Automatic email alerts when anomalies occur, with cooldown periods to prevent spam

Your RPC Monitor Dashboard:
┌─────────────┬──────────┬─────────┬────────────┐
│ Name        │ Status   │ Latency │ Last Block │
├─────────────┼──────────┼─────────┼────────────┤
│ Ethereum #1 │ ✅ Online│ 45ms    │ 19876543   │
│ BSC Mainnet │ ❌ Offline│ timeout│ -          │
│ Polygon     │ ⚠️ Stuck │ 120ms   │ 54321000   │
└─────────────┴──────────┴─────────┴────────────┘

✅ Smart Alerts: Non-Intrusive But Never Misses Critical Issues

Node goes from online to offline → Instant alert
Block height stops updating → Instant alert
Cooldown period prevents duplicate messages → No email spam
Manual trigger support → Verify node status anytime

✅ 500+ EVM Chains, One Dashboard

From Ethereum, BSC, and Polygon to Arbitrum, Optimism, Base, plus countless Layer 2s and testnets — you can monitor RPCs on all EVM-compatible chains. Manage all your nodes from a single dashboard. No more juggling multiple platforms.

🚀 Who Needs RPC Monitor Most?

Role	Core Need	RPC Monitor's Value
DApp Developers	Keep user transactions smooth	Detect RPC failures instantly, switch to backup nodes fast
DeFi Protocol Teams	Multi-RPC failover	Monitor multiple RPCs simultaneously, get alerted on failures
MEV Searchers / Trading Bots	Ultra-low latency	Precise millisecond latency data to pick optimal nodes
NFT Projects	Stability during high-traffic mints	Monitor block height, prevent stuck blocks from breaking mints
Exchanges / Custodians	Node sync status	Continuously verify block height, ensure nodes stay synced

🎯 Real Scenario: From "Reactive Firefighting" to "Proactive Defense"

Before RPC Monitor:

User: "Why is your DApp spinning forever?"
You: "Hold on, let me check... looks like the RPC is down. Let me switch nodes."
User: "I've been waiting for half an hour!"

After RPC Monitor:

📧 Email Alert: "Ethereum Mainnet RPC is offline. Error: connection timeout"
You: (Receive alert, switch to backup node within 5 minutes)
User: (Zero disruption, transactions continue smoothly)

🔧 Get Started in 2 Minutes

Visit rpchub.top
Connect your wallet to log in
Add the RPC endpoints you want to monitor (name + URL + chain ID)
Setup complete — monitoring starts automatically
Get instant email notifications when anomalies occur

Two minutes of setup saves you from countless late-night emergency debugging sessions.

💎 Why Choose RPC Hub?

Free to use: Core features are completely free
Open source & transparent: Code is open, data stays under your control
Professional & accurate: Server-side probing + block verification, double protection
Continuously improving: Active development with regular feature updates

📢 Final Thoughts

In Web3, stability is your competitive edge. Your users don't care about "the RPC node went down" — they just know your DApp doesn't work.

Spend 2 minutes setting up RPC Monitor, and you get:

✅ 7×24 hands-off monitoring
✅ Instant failure detection
✅ Zero user complaints
✅ Peace of mind and a good night's sleep

Head over to rpchub.top and try it now. Your future self will thank you.

Found this article helpful? Share it with more Web3 developers. Got questions? Drop them in the comments!

How Web3 Developers Can Find the Fastest, Most Reliable RPC Nodes

kilozz — Fri, 25 Sep 2026 07:00:38 +0000

If you're a Web3 developer, you've definitely run into these situations:

Transaction stuck pending for ages, only to find the RPC node is down
eth_call timing out repeatedly, but switching to a different node returns instantly
Infura free tier exhausted, and finding a replacement feels like searching for a needle in a haystack
Chainlist says a node is "online," but every request you send throws errors

RPC node quality directly impacts your DApp's user experience and development velocity. So how do you actually find a fast and reliable RPC? This guide walks you through it — from first principles to practical tooling.

Disclosure: I use RPC Hub in my daily workflow and contribute to the project. The first half of this post is framework-agnostic — the principles apply regardless of which tool you use to evaluate RPC nodes.

1. Why Are Good RPCs So Hard to Find?

Let's start with a fundamental insight: RPC node quality is not static.

A node that's fast today may not be fast tomorrow. A node that works well for users in the US might be slow for users in Asia. And a node that returns eth_blockNumber just fine might time out on eth_getLogs.

Worse still, most RPC directories — including Chainlist — have a fundamental flaw in how they detect node health:

Browser-side detection → CORS restrictions → massive false "offline" reports

When you fetch an RPC URL from the browser, if the provider hasn't configured CORS headers, the request gets blocked by the browser — even though the node itself is running perfectly. This is why Chainlist often shows nodes as "offline" when they're actually fine.

Reliable detection must happen server-side.

2. Three Core Metrics for Evaluating RPC Nodes

In order of importance:

1. Latency

This is the most intuitive metric. Lower latency means faster transaction confirmations and quicker eth_call responses. Here's a rough guide:

Latency	Experience
< 50ms	Excellent — suitable for HFT / MEV
50–150ms	Good — perfectly fine for daily development
150–500ms	Usable, but your DApp frontend will feel sluggish
> 500ms	Avoid — poor user experience

But latency isn't everything. Some nodes have low latency but miss blocks (see below).

2. Block Height

A node could have 10ms latency, but if it's 10 blocks behind, the on-chain data you're reading is stale. This is fatal in DeFi scenarios — you might think the price hasn't changed when someone already front-ran you.

So when probing a node, you must verify all three:

Is the node online?
What's the latency in milliseconds?
Is the block height caught up with the network?

3. Privacy Policy

Many free RPC nodes log your request data. That might not matter for a solo developer, but if you're:

Running MEV or trading strategies
Handling sensitive user data
Operating under strict compliance requirements

Then you need to know: does this RPC provider log, analyze, or resell your request data?

3. How to Find the Best RPC — The Practical Way

Theory is great, but how do you actually do this? The old-school approach — curl each endpoint one by one — is painfully slow. You need a more efficient workflow.

Here's how to do it in one place, using RPC Hub as an example.

500+ EVM Chains Covered

Whether you're working with Ethereum, BSC, Polygon, Arbitrum, Optimism, or niche L2s/L3s, you'll find the corresponding RPC list. The data is sourced from chainlist.org's ethereum-lists/chains repository (EIP-3770 standard), with significant enhancements on top.

Server-Side Real-Time Probing

This is the key differentiator. RPC Hub probes endpoints from the server side, completely bypassing browser CORS restrictions. Each node returns three data points:

Online status — real online/offline, no false positives
Latency — millisecond-level precision
Block height — verifies sync is healthy

RPC Score Comparison

A single chain often has a dozen RPC providers. RPC Hub ranks them all, giving a composite score based on latency and availability. You can see at a glance which one is fastest and which one is most stable — no manual trial and error.

Privacy Transparency

Every RPC provider is tagged with its privacy policy (tracking info), so you know exactly what data collection behavior to expect.

One-Click Add to Wallet

Found a good one? One click adds it to MetaMask — no more manually filling in Chain ID, RPC URL, Currency Symbol, and Block Explorer URL.

4. More Than Just RPC Discovery: Built-in Dev Tools

RPC Hub isn't just an RPC directory. It also packs several practical development tools:

JSON-RPC Playground

Send raw JSON-RPC requests directly in the browser, with method presets for common calls:

Category	Methods
Network	`net_version`, `eth_chainId`, `eth_blockNumber`, `eth_syncing`
Account	`eth_getBalance`, `eth_getTransactionCount`, `eth_getCode`
Block	`eth_getBlockByNumber`, `eth_getBlockByHash`
Transaction	`eth_getTransactionByHash`, `eth_getTransactionReceipt`
Gas	`eth_gasPrice`, `eth_maxPriorityFeePerGas`, `eth_feeHistory`, `eth_estimateGas`

Requests are proxied through the server, so there are no CORS issues. You can also export any request as a cURL command for local reproduction.

Cast Terminal

Foundry's cast is the Swiss Army knife of on-chain development, but switching to a terminal every time is a friction point. RPC Hub's Cast Terminal lets you run cast commands right in the browser — cast block-number, cast balance, cast call — with instant results.

Safety guardrails: cast send and cast wallet are blocked to prevent accidents.

ABI Codec

Encode and decode EVM calldata, supporting all Solidity types including tuples and arrays. Invaluable for debugging contract call parameters.

Faucet Directory

A curated list of testnet faucets organized by network, so you don't have to hunt around during development.

5. RPC Hub vs. Chainlist

Dimension	Chainlist	RPC Hub
Detection Method	Browser-side fetch	Server-side multi-node probing
CORS Limitations	Yes — many false reports	None
Latency Data	None	Multi-region real-time latency
Historical Data	None	Full time-series data
Provider Verification	None	Badge system
Alerting	None	Multi-channel notifications

6. Summary

Back to the original question: How do Web3 developers find the fastest, most reliable RPC nodes?

Don't just check online status — latency and block height matter just as much
Don't trust browser-side detection alone — CORS will give you false results
Use a tool that does it all in one place — the time you save is better spent shipping code

RPC Hub is completely free and collects zero user data — which is how I believe infrastructure tooling should be built. If you have a workflow for RPC selection that works for you, I'd love to hear about it. And if you try RPC Hub, feedback and contributions are always welcome 👉 rpchub.top

Originally published on Dev.to. Feel free to repost with attribution.