cside vs Sift: 2026 comparison

Sift is a fraud-decisioning platform that scores transactions; cside is a client-side security and first-party signal product. They aren't the same tool, here's where they overlap, and why a first-party approach to device signals matters.

Jun 19, 2026 • Updated Jul 19, 2026

Simon Wijckmans Founder & CEO

TL;DR: cside vs Sift

Sift is mature ML fraud decisioning with one of the largest fraud graphs in the industry. Its signals are predominantly server-side: transactions, identity events, network attributes.
cside collects device and behavioral signals from your own first-party JavaScript at the browser layer, capturing the Visa CE 3.0 device continuity evidence Sift's model does not surface, plus AI agent detection, AI-generated-text detection, and PCI DSS 6.4.3 and 11.6.1.
Want ML-based fraud scoring on transactions and identity: Sift. cside covers the browser layer and device evidence it does not produce. Most teams run both.

What is Sift?

Sift is an AI-powered, score-based fraud-decisioning platform covering payment fraud, account takeover, content abuse, and dispute management, founded in 2011 in San Francisco. It consumes client-side signals through a third-party JavaScript collector and business events through a server-side API, then returns a 0-100 risk score per abuse type; the customer owns the decision and the loss. It's a mature product with strong, well-established G2 ratings and a large customer base in marketplaces, fintech, and on-demand commerce.

How Sift works

Sift's browser snippet (cdn.sift.com/s.js, a global window._sift object, and a long-lived __ssid cookie) plus mobile SDKs collect device and behavioural signals; your backend posts events to Sift's Events API; machine learning returns a score, and Workflows route accept / block / review decisions that you feed back for training.

Two things follow from that design that matter for a client-side security buyer. First, the collector is a third-party script with a fixed, well-known origin, it sits on the EasyPrivacy filter list and is blocked by default in common ad blockers, so the browser-collected signal degrades for privacy-conscious users (the server-side Events API signal still flows). Second, that collector is itself an unmonitored third-party script on your pages, precisely what PCI DSS 6.4.3 asks merchants to inventory and watch.

How cside fits

cside isn't a replacement for Sift's fraud decisioning, and we won't pretend otherwise. What cside does is the layer underneath and around it.

cside collects device and behavioural signals from your own first-party JavaScript, so there's no third-party origin for a filter list to block and no fixed collector for a fraudster to detect and feed. It produces device fingerprinting with bot and AI agent detection, and it gives you evidence you own, usable in chargeback disputes through our Chargebacks911 integration.

And cside does the thing Sift doesn't: it inventories, justifies, and tamper-monitors every script on your payment pages, including collectors like Sift's, to satisfy PCI DSS 6.4.3 and 11.6.1, with a QSA-validated dashboard and immutable payload archives. Many teams run a decisioning platform and cside together; if the device-signal layer or PCI script coverage is your gap, that's where cside fits.

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Related resources

Founder & CEO Simon Wijckmans

Founder and CEO of cside. Previously a product manager on Cloudflare Page Shield (now Cloudflare Client-Side Security). Co-chair of the W3C Anti-Fraud Community Group and a Forbes 30 Under 30 honoree. Building accessible security against client-side attacks, web security is not an enterprise-only problem.

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FAQ

Frequently Asked Questions

Only partly. Sift is an AI fraud-decisioning platform: it ingests signals and returns a 0-100 risk score for payment fraud, account takeover, and abuse, and the customer acts on it. cside is a client-side security and first-party device-signal product. They overlap on the device / JavaScript signal layer, but cside does not do fraud decisioning, dispute automation, or content moderation, and Sift does not police the scripts on your pages. For many teams they're complementary.

Sift's client-side collector domains are on the EasyPrivacy filter list (`||sift.com^$third-party` and `||siftscience.com^$third-party`), which is bundled by default in uBlock Origin and AdBlock Plus. For visitors using those tools, the in-browser collector doesn't load, so Sift's device intelligence degrades and can produce false positives on privacy-conscious but legitimate users. Server-side signals sent through Sift's Events API still flow, it isn't blind, but the browser-collected portion is affected. cside collects signals from your own first-party JavaScript, so there is no third-party origin for a filter list to block.

No. Sift is not a script-security product and does not address PCI DSS 6.4.3 / 11.6.1. In fact, Sift's own collector is exactly the kind of third-party script that requirement 6.4.3 makes a merchant inventory and monitor. cside is built to inventory, justify, and tamper-monitor every script on your payment pages, including collectors like Sift's.

Sift sells a risk score; the customer owns the decision, and there is no chargeback guarantee, so the merchant retains the liability for a wrong score. cside is a signal and evidence layer rather than a decisioning engine, it gives you device and behavioural evidence you own and can use, including in chargeback disputes.