Prediction markets let you trade on the outcome of real events — elections, economic data, crypto prices, whether a CEO resigns. You buy contracts that pay $1 if you’re right, $0 if you’re wrong. Polymarket and Kalshi are the two biggest.
"Will the Fed cut rates in March 2026?"
┌─────────────────────────────────────┐ │ YES $0.62 ← 62% chance │ │ NO $0.38 ← 38% chance │ │ ─────── │ │ $1.00 │ │ │ │ Buy YES at 62¢ → pays $1 if right │ │ Buy NO at 38¢ → pays $1 if right │ └─────────────────────────────────────┘Simple enough. But neither Polymarket nor Kalshi shows you what other traders are doing. Large trades happen constantly on both platforms, but unless you’re watching the right market at the right moment, you miss them. You see the price change after the fact and have no idea what caused it.
I kept running into this. So I built 0xInsider.
It’s a real-time terminal that shows every large trade on Polymarket and Kalshi as it happens. Both platforms, one feed.
TIME SIDE TRADER MARKET SIZE PRICE ──────────────────────────────────────────────────────────────────────────────────── P 3s ago BUY CryptoWhale... Will BTC hit $120k by Apr? $23,400 42¢ K 8s ago BUY Anonymous Fed rate hold in March? $31,500 84¢ P 12s ago SELL degen_0x42... Next Supreme Court retirement? $18,100 61¢ K 15s ago BUY Anonymous Unemployment rate Jan 2026? $34,485 95¢ P 19s ago BUY polywhale... GDP growth above 3%? $27,000 38¢Trades stream in via server-sent events. No polling, no refreshing.
What you actually see
The two platforms give you very different levels of detail.
Polymarket is on-chain. Every trade is tied to a wallet address, so I can show the trader’s history — win rate, total P&L, number of markets traded, and a performance grade.
Polymarket trade:
┌──────────────────────────────────────────┐ │ BUY $23,400 — Will BTC hit $120k? │ │ │ │ Trader: CryptoWhale... Grade: A │ │ Win rate: 71% Markets: 143 │ │ Total P&L: +$284,500 │ │ Recent: 4/5 wins │ │ │ │ → View full profile │ └──────────────────────────────────────────┘A $23K trade from someone with a 71% win rate across 143 markets reads differently than the same trade from a new wallet with no history. Doesn’t mean the first one is right — but it’s useful context.
Kalshi is different. It’s a centralized, CFTC-regulated exchange. Trades are anonymous — no user IDs, no wallet addresses. You see the size, the price, and the direction, but not who. That’s how Kalshi works. Their API doesn’t expose trader identities.
Kalshi trade:
┌──────────────────────────────────────────┐ │ BUY $31,500 — Fed rate hold in March? │ │ │ │ Trader: Anonymous │ │ Kalshi does not reveal trader identities │ │ │ │ → View market on Kalshi │ └──────────────────────────────────────────┘What matters is you see the trade at all. Before this, Kalshi whale activity was invisible unless you happened to be staring at that exact market.
What large trades can tell you
Large trades don’t predict the future. Someone dropping $30K on an outcome might have great research, or they might be wrong. But they do tell you something: someone with real money has conviction about a specific outcome at a specific price.
Here’s a situation I kept noticing:
Without a trade feed:
t=0s Someone buys $30K YES at 42¢ │ t=30s Price ticks to 44¢ │ t=5min Price settles around 47¢ │ t=10min You check the market. See 47¢. No idea what moved it.
With a trade feed:
t=0s Someone buys $30K YES at 42¢ │ t=2s Trade appears in your terminal │ Now you know what happened. Whether you act on it is up to you.The information was always there. It just wasn’t surfaced anywhere.
Some traders also watch for pricing differences when the same event is listed on both platforms. If YES trades at 58¢ on Kalshi and 52¢ on Polymarket, that gap might mean something — or it might just be different liquidity. But you can’t evaluate it if you can’t see both sides.
The terminal is at 0xinsider.com. It’s currently in beta — if you want early access, join the Discord and ask. We’re also posting trade highlights and updates on X/Twitter.