can-decode

can-decode is a cursor rule for Cursor from ratnesh-maurya/cursor-claude-personas. It costs 14 tokens per session (401 once invoked), scanned A, original, MIT.

A Mediabunny utility that checks whether a browser can read and decode a video's audio and video tracks.

In plain words
What is it for?
Use it to validate videos from URLs, uploads, or drag-and-drop files before playback.
Why use it?
It lets an application detect unsupported media before trying to play it.

Cursor rule for Cursor

Written for Cursor: installed under .cursor/.

Good fit Use it to validate videos from URLs, uploads, or drag-and-drop files before playback.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/ratnesh-maurya/cursor-claude-personas/rules-can-decode
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/ratnesh-maurya/cursor-claude-personas

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for can-decode

README.md
[![agentmods](https://agentmods.dev/badge/rules/ratnesh-maurya/cursor-claude-personas/rules-can-decode/github.svg)](https://agentmods.dev/rules/ratnesh-maurya/cursor-claude-personas/rules-can-decode)
Your own site
<a href="https://agentmods.dev/rules/ratnesh-maurya/cursor-claude-personas/rules-can-decode"><img src="https://agentmods.dev/badge/rules/ratnesh-maurya/cursor-claude-personas/rules-can-decode/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for can-decode

Your own site · 80×15
<a href="https://agentmods.dev/rules/ratnesh-maurya/cursor-claude-personas/rules-can-decode"><img src="https://agentmods.dev/badge/rules/ratnesh-maurya/cursor-claude-personas/rules-can-decode.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 14 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 401 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00014 $0.00401
Opus 5 $0.00007 $0.00200
Sonnet 5 $0.00003 $0.00080
Haiku 4.5 $0.00001 $0.00040

Measured 5d ago against content hash fb3f9933e451, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

can-decode scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

3d-frontend-developer/.cursor/rules/rules--can-decode.mdc · 76 lines

What it actually says

Checking if a video can be decoded

Use Mediabunny to check if a video can be decoded by the browser before attempting to play it.

The canDecode() function

This function can be copy-pasted into any project.

import { Input, ALL_FORMATS, UrlSource } from "mediabunny";

export const canDecode = async (src: string) => {
  const input = new Input({
    formats: ALL_FORMATS,
    source: new UrlSource(src, {
      getRetryDelay: () => null,
    }),
  });

  try {
    await input.getFormat();
  } catch {
    return false;
  }

  const videoTrack = await input.getPrimaryVideoTrack();
  if (videoTrack && !(await videoTrack.canDecode())) {
    return false;
  }

  const audioTrack = await input.getPrimaryAudioTrack();
  if (audioTrack && !(await audioTrack.canDecode())) {
    return false;
  }

  return true;
};

Usage

const src = "https://remotion.media/video.mp4";
const isDecodable = await canDecode(src);

if (isDecodable) {
  console.log("Video can be decoded");
} else {
  console.log("Video cannot be decoded by this browser");
}

Using with Blob

For file uploads or drag-and-drop, use BlobSource:

import { Input, ALL_FORMATS, BlobSource } from "mediabunny";

export const canDecodeBlob = async (blob: Blob) => {
  const input = new Input({
    formats: ALL_FORMATS,
    source: new BlobSource(blob),
  });

  // Same validation logic as above
};
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 76 lines · 14 tokens per session scan A fb3f9933e451

Subscribe to this mod's changes

can-decode is a cursor rule published in the GitHub repository ratnesh-maurya/cursor-claude-personas (8 stars, last pushed 5mo ago), licensed MIT. It adds 14 tokens to every session and 401 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.