Is this code safe?

Is this HTML safe?

Paste code before you run it. We'll explain what it does and flag suspicious behavior.

Examples:

Paste code on the left and press Check Code.

The scanner reports:

  • network requests and the hosts they contact
  • file reads, writes and deletions
  • shell command execution
  • code built and executed at runtime
  • access to cookies, credentials, clipboard and keystrokes
  • persistence, privilege changes and security tool tampering
  • encoded payloads and obfuscation

Findings are separated into capabilities (what the code can do) and suspicious behaviour (patterns typical of malicious scripts), because using the network is not the same as stealing data.

Static checks run locally in your browser. Nothing is uploaded, logged or stored.

Press Ctrl/Cmd + Enter to check.

How it works

Paste a page, an email template or an embed snippet. Every tag is scanned with its source position, and inline script blocks are parsed as JavaScript so findings point at the exact line.

  1. The language is detected from the code, and you can override it in the dropdown.
  2. JavaScript and TypeScript are parsed into an abstract syntax tree, so function calls, imports and property accesses are matched structurally rather than as text. Python, PowerShell and shell are scanned with rules that first mask comments and string contents. HTML is scanned tag by tag, with inline scripts handed to the JavaScript analyzer.
  3. Findings are split into capabilities (what the code can do) and suspicious behaviour (patterns typical of malicious code).
  4. Behaviour chains are evaluated: reading cookies is one thing, reading cookies and posting them to a hardcoded host is another.
  5. A risk level is assigned, every finding links to its line, and you can optionally ask an AI model to explain the result in prose.

What it detects

  • scripts loaded from external domains, and scripts embedded as base64 data URIs
  • inline event handlers such as onload and onerror
  • forms that post to another domain, and password fields inside them
  • iframes sized to zero or hidden with CSS
  • javascript: URLs in href, src and action attributes
  • meta refresh redirects and base href rewrites
  • everything the JavaScript checker finds, applied to inline scripts

Privacy: your code stays in your browser

The whole static analysis, including parsing, rule matching and risk scoring, is compiled into the page and runs on your machine. No request is made when you press Check Code, nothing is logged and nothing is stored. The only exception is the optional AI explanation: it is off by default, and when you tick the box the code is sent to the configured AI provider for that single request.

Why we never say "this code is safe"

Nobody can prove a piece of code is harmless by inspecting it. Code can fetch its real payload at runtime, behave differently on another machine, or hide its intent in a dependency you cannot see. So the verdict is always one of four: low apparent risk, potential risk, high risk, or unable to determine. "Low apparent risk" means these particular patterns are absent — nothing more.

Frequently asked questions

What makes a form look like phishing?
A password field inside a form whose action points at a different domain. That is the structural signature of a credential harvesting page, and it is reported as high risk.
Are external scripts always a problem?
No, but they mean another party can run any code they want in the page, and can change that code at any time. The checker names the host so you can decide whether you trust it.

Checkers by language