Why I Built a Free Crypto Screener

A dev's honest account of 3 months of frustration, late nights, and one question that wouldn't go away: why does every useful trading tool cost $100/month?

I used to spend the first 20 minutes of every trading session doing the same boring ritual.

Open one tab. Check BTC. Open another. Check ETH. Open another. Check SOL. Scroll through a list of 50 coins manually, one by one, trying to spot something moving with volume behind it. By the time I finished, whatever I was looking for had already moved.

It wasn't a strategy problem. It was a visibility problem.

The market has 500+ tradeable coins on any given day. No human can watch all of them at once. But finding a tool that actually solved this — not a watered-down free tier with 3 coins visible, not a $149/month subscription — turned out to be harder than I expected.

So I built one myself. And then I put it online for free. Here's why.

The Part Where I Realized I Was Wasting Time

I'm a developer. I've been trading crypto on and off since 2020. For a long time I didn't connect those two things — I just used whatever tools everyone else used.

But I started paying closer attention to where my losses were actually coming from. And a pattern showed up: I wasn't making bad trades because my strategy was wrong. I was making bad trades because I was late. I'd read about a coin that had already moved 8%. I'd enter a position without realizing volume had already dried up. I'd miss a setup entirely because I wasn't watching the right place.

The information was all there in the market. I just had no way to filter it fast enough.

I looked at the paid tools. Some of them are genuinely good. But $50-200/month adds real pressure to your trading. You're now not just trying to make money — you're trying to cover your tool costs first. That changes how you trade. It makes you force setups that aren't there.

I didn't want to pay for that pressure. So in late 2024, I started building.

What "Real-Time" Actually Means (And Why It Changes Everything)

The first thing I figured out pretty quickly: the difference between a useful screener and a useless one is almost entirely about data freshness.

A screener showing you data from 15 minutes ago is basically a history lesson. By the time you see a volume spike, act on it, and enter a position, the move has already happened. You're not trading the setup — you're trading the aftermath.

Real-time WebSocket data changes this. Instead of polling an API every minute and hoping nothing important happened in between, WebSocket connections stream price and volume updates as they happen. Milliseconds, not minutes.

That was the architecture I needed: coins updating live, signals calculating in real time, the screener always showing you what's happening right now — not what happened a few minutes ago.

Volume plus price movement creates patterns. That's not a secret. What's rare is being able to see those patterns as they form, across 500+ coins, without spending half your morning checking tabs manually.

The Technical Part (I'll Keep It Short)

The stack ended up being Node.js on the backend with WebSocket connections to four exchanges: Binance, Bybit, Coinbase, and OKX. MySQL for storing candle data and pre-calculated signals. A React frontend that updates in real time.

Sounds simple. It wasn't.

WebSocket stability was the first real problem. Exchanges drop connections. They throttle you. They send malformed messages at weird times. The first version of the backend would just silently die, and I wouldn't know until I checked the data 2 hours later and noticed nothing had updated. I ended up building reconnect logic with exponential backoff and heartbeat monitoring — boring infrastructure work, but without it the whole thing falls apart.

Data sync across exchanges was messier than I expected. Binance and Bybit have slightly different data formats, different timestamps, different ways of handling trading pairs. Getting candles from all four exchanges into a consistent schema, without gaps or duplicates, took a few weeks of trial and error.

Database scaling became a real concern fast. When you're storing candle data for 500+ coins across multiple timeframes, the rows pile up quickly. Query performance tanks if you're not careful about indexing. I spent time building a pre-filtering step that runs calculations before the API ever gets called, so the frontend isn't waiting on heavy queries.

None of this was glamorous. But it's what makes the tool actually reliable.

Why I'm Not Charging for It

Honestly? A few reasons.

The paid tools already exist. If I launched another $100/month screener, I'd be competing in a crowded market against products with years of development behind them. That's not a fight I'm interested in.

But more than that — I think the paywall model is the wrong one for this kind of tool. Day traders are already paying exchange fees, funding rates, spread. Adding a mandatory subscription on top of that, just to see which coins are moving, feels like the wrong direction.

I want devisecrypto.com to be the thing you open automatically when you sit down to trade. Not the thing you cancel when you have a bad month.

If the community around it grows, there are other ways to build something sustainable. But making the screener itself free wasn't a compromise — it was the whole point.

What's Live Right Now

You can go to devisecrypto.com right now — no account needed for the core screener. Sign up free to get access to extra features::

Real-time data from Binance, Bybit, Coinbase, and OKX
Pre-built technical filters — volume surges, RSI signals, EMA crossovers, Bollinger Band touches, and more
Sorting by volume change, price change, market cap — so you can immediately see which coins are moving and which are sitting still
Multi-timeframe support — 5m, 15m, 1h, 4h, daily

The core screener is completely free — no trial period, nothing locks after 7 days. Create a free account to unlock additional features like watchlists and personalized filters, or just use it as-is without signing up. Either way, the real-time data and filters are there from the moment you open it.

What Comes Next

The screener is working. The data pipeline is stable. But there's more I want to build — alerts, watchlists, more filter combinations, better mobile experience.

If you use it and something's broken or missing, I actually want to know. This isn't a corporate product with a support queue. It's something one developer built because he needed it, and decided to share.

Try it: devisecrypto.com

If you're also a developer who's built trading tools, or a trader who's sick of paying for screeners, I'd genuinely like to hear what you think in the comments.

Built with love and too much coffee.

— The dev behind DeviseCrypto