Hey dev.to — Pennyforge here, a one-person studio that builds small, useful tools that replace SaaS. Today I'm sharing our first product: SendCheck, a free tool that checks a crypto address before you send, so the worst-case finding is "looks wrong" instead of "your USDC is gone".
The pain
Sending crypto is one-way. Paste the wrong address, or send USDC on a network the receiving exchange doesn't listen to, and there is no support ticket and no undo. I kept seeing the same story in crypto help communities: hundreds of dollars, one wrong paste, gone. So I built the check I wished I had, runnable in a few seconds in the browser.
What it checks (free, no account)
- Format + checksum: is it a valid address for the chosen chain, and is the casing EIP-55-correct?
- Has it ever been used? A nonce check against public RPC. A never-used address earns a caution, not an error (receive-only addresses legitimately sit at nonce 0), but it is good to know before your savings are the first thing it ever holds.
- Contract or wallet? Every address gets labelled as one or the other, so sending to a contract happens on purpose.
- USDC variant check: on Base, USDC and bridged USDC.e have different addresses and different behavior; the tool tells you which one you are looking at, on every network it supports.
- Rail watch: per-exchange, per-token, per-network support matrix (Coinbase, Kraken, Binance, OKX, Gemini, Bybit), with a confidence rating on every cell, dated change entries, and sources.
How it works
Everything runs in your browser. The page talks directly to public RPC endpoints for Base, Ethereum, Arbitrum, Optimism and Polygon, and cross-checks against a curated table of canonical token addresses. Your address never touches our servers; the whole site is static.
Pro (0.50 USDC, one-time)
Free gets you three checks a day; Pro is unlimited checks on this browser for 0.50 USDC, once. Pay in USDC and we verify it on-chain: the check reads the USDC Transfer logs of your transaction and confirms the USDC actually reached our wallet. No screenshots, no trust. Refund = the exact USDC back to your address, on-chain.
Sharing
Every check gets a share link. The link is a pointer, not a snapshot: whoever opens it gets a fresh, live re-run in their own browser, and shared checks are free for them. It turns "here's a screenshot of what I found" into "here, run it yourself".
Try it: https://sendcheck.surge.sh
Feedback is welcome — I read every comment. And if it ever catches a bad address before you lose money, the tip section at the bottom of the page (USDC on Base) is real, but the "it caught it" replies mean more.
