About Castle
Castle provides developer-grade infrastructure to stop bots, abuse, and fraud. It turns user behavior into real-time signals used by companies such as Canva, Rockstar Games, and Atlassian. Its platform includes IP intelligence, device fingerprinting, bot detection, AI scoring, behavioral analysis, email intelligence, and case and state management.
Castle describes itself as profitable and product-led. Its AI scoring is meant to spot account takeover attempts and abusive behavior. Its IP intelligence assesses IP reputation and risk and detects proxies, VPNs, Tor, and datacenter traffic.
Castle's investors include Index Ventures at Series A, and Y Combinator and First Round Capital at seed. Y Combinator is listed with the W16 batch.
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Recently
From Castle's own newsroom feed and from the hiring team.
La majorité du trafic internet n’est pas humaine: comprendre les botsFrom their feed
🇫🇷 Note: This blog post is written in French. I’m publishing it alongside a video I did with Micode, a French YouTuber, so it felt more natural to share this content in French as well. Je profite de la sortie de ma vidéo avec Micode/
September 21, 2026
What sits behind a “private” proxy networkFrom their feed
NexaProxies describes itself as a “Private proxy network. Access by invitation only.” That wording made us curious. Does “private” also mean that the underlying residential IPs are unique to NexaProxies, or are the same IPs available through other proxy providers too? We recently got access and
September 17, 2026
Two chicken nuggets and a Claude accountFrom their feed
A few days ago I saw a screenshot on X of someone talking to what looks like a McDonald's support chatbot. They wanted to order Chicken McNuggets, but before that they asked the bot to write a Python script to reverse a linked list. The screenshot is probably
September 10, 2026
While anti-bot vendors talk about AI agents, classical bots are getting the bypassesFrom their feed
⚠️ A quick disclaimer on AI agent management AI agents will clearly change how people interact with websites. They will search, compare products, make purchases, fill forms, and perform actions that used to require a human in front of a browser. Websites will need ways to decide which agents
September 3, 2026
We're unbundling Castle, and IP intelligence is the first pieceFrom their feed
Castle is becoming two things. There's the platform, which watches a session and decides for you, and there's the intelligence underneath it, which you can now buy on its own. The IP intelligence API is live today, free to sign up, and $0.001 per
August 12, 2026
Will prediction markets turn your platform into a bot target?From their feed
Prediction markets can give bots a direct financial incentive to manipulate online metrics. TL;DR Prediction markets such as Polymarket and Kalshi let people bet on future events, from election results to sports outcomes. Some markets are resolved using metrics published by websites and applications: Spotify streams, Twitch views, public
August 5, 2026