Test a crypto strategy before you trust it
Build a rule-based strategy with no code, backtest it on real daily prices with fees and slippage, see how it did on data it was not tuned on, then run it as a paper bot that alerts you on every trade it would make. Free for BTC and ETH.
1. Build
Costs and test split
Every fill pays the fee and the slippage. The last part of the period is out-of-sample: judge a strategy on that part, not on the part you tuned it on.
2. Results
Trades
3. Paper bots
A paper bot runs your strategy on live daily prices with pretend money, using the same engine as the backtest. After each daily close (00:00 UTC) it decides, and you get an alert for every trade it would make. Nothing is ever traded. Free: 1 bot. Pro: 25.
How the backtest works
Prices are daily candles from exchanges' public market data (Bitstamp, or Coinbase when Bitstamp does not list the coin), loaded straight into your browser. A strategy only sees closed days: it decides after a day closes and the trade fills at the next day's open, plus slippage and minus the fee. Results show the whole period, the in-sample part and the out-of-sample part, each beside buy-and-hold with the same costs.
Strategies: DCA (a fixed amount on a schedule, optional take-profit), grid (buy at levels in a range, sell one level up), moving-average cross (SMA or EMA), RSI bands, rebalancing to a target mix, trailing stop. Spot only: no leverage, no shorting. Daily bars only, so intraday moves inside a day are not seen.
Information only, not financial advice. Backtests describe the past; past results don't guarantee future results. Trading involves risk of loss. Backlark never trades and never asks for keys.
Questions
Does a good backtest mean the strategy will make money?
No. It shows how fixed rules would have behaved on past prices. A strategy tuned to the past often fails on new data, which is why the out-of-sample result, the worst drop and buy-and-hold are always on screen. The parameter sweep warns you when the best in-sample settings do worse out of sample.
Can it trade for me?
Backlark never trades. Export your strategy and run it in Helmwick, a program you download and run on your own computer with your own exchange keys (paper and testnet first; your keys never reach us).
Why not 3Commas, Cryptohopper or Coinrule?
They run live bots on your exchange account and are priced for it: Cryptohopper Explorer $29 a month, Coinrule's first paid plan $29.99 a month, 3Commas from about $22 to $29 a month (checked 31 Oct 2026). Backlark is the honest testing bench: free for BTC and ETH, $9 a month for everything.
Where does the price data come from?
Exchange public market-data endpoints (Bitstamp and Coinbase), fetched by your browser and kept in your browser for 12 hours. Prices differ slightly between exchanges.