Deno is a runtime that executes JavaScript, TypeScript, and WebAssembly programs outside a browser. Developers use it for applications such as web servers, and the catalogue add-ons provide workflows and guidance for Deno projects.
Borrowing it
Nothing to install: this file belongs to denoland/deno. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/denoland/deno/main/.github/copilot-instructions.mdgit clone --depth 1 https://github.com/denoland/denoWrote 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.
[](https://agentmods.dev/instructions/denoland/deno/copilot-instructions)<a href="https://agentmods.dev/instructions/denoland/deno/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/denoland/deno/copilot-instructions/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.
<a href="https://agentmods.dev/instructions/denoland/deno/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/denoland/deno/copilot-instructions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.03077 | $0.03077 |
| Opus 5.5 | $0.01231 | $0.01231 |
| Sonnet 5.5 | $0.00615 | $0.00615 |
| Haiku 4.5 | $0.00308 | $0.00308 |
Grade A, and why
deno copilot-instructions.md 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 353 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Deno Development Guide for GitHub Copilot
Network Access
The development tools in this repository need network access to function. When
running tools/format.js or tools/lint.js, ensure the following domains are
reachable:
https://jsr.io— Deno's package registry, used for@std/*importshttps://dprint.devandhttps://plugins.dprint.dev— the formatter (tools/format.js) runsnpm:dprintwhich downloads WASM plugins fromplugins.dprint.dev
If you are running in a sandboxed environment, you must allowlist these domains or the tools will fail with network errors.
High Level Overview
The user-visible interface and high-level integration is in the deno crate
(located in ./cli).
This includes flag parsing, subcommands, package management tooling, etc. Flag
parsing is in cli/args/flags.rs. Tools are in cli/tools/<tool>.
The deno_runtime crate (./runtime) assembles the JavaScript runtime,
including all of the "extensions" (native functionality exposed to JavaScript).
The extensions themselves are in the ext/ directory, and provide system access
to JavaScript — for instance filesystem operations and networking.
Key Directories
cli/— User-facing CLI implementation, subcommands, and toolsruntime/— JavaScript runtime assembly and integrationext/— Extensions providing native functionality to JS (fs, net, etc.)libs/— Shared Rust crates (core, resolver, npm, node_resolver, serde_v8, etc.)tests/specs/— Integration tests (spec tests)tests/unit/— Unit teststests/testdata/— Test fixtures and data files
Key Files to Understand First
cli/main.rs— Entry point, command routingcli/args/flags.rs— CLI flag parsing and structureruntime/worker.rs— Worker/runtime initializationruntime/permissions.rs— Permission systemcli/module_loader.rs— Module loading and resolution
Common Patterns
- Ops — Rust functions exposed to JavaScript (in
ext/directories) - Extensions — Collections of ops and JS code providing functionality
- Workers — JavaScript execution contexts (main worker, web workers)
- Resources — Managed objects passed between Rust and JS (files, sockets, etc.)
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.
- 1mo ago First seen · 353 lines · 3,077 tokens per session scan A 3ecf3a02d8dc
deno copilot-instructions.md is an instructions file published in the GitHub repository denoland/deno (108,724 stars, last pushed today), licensed MIT. It adds 3,077 tokens to every session, about $0.0123 per session on Opus 5.5. 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 2026-08-30.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
generative-ai-for-beginners AGENTS.md
AGENTS.md instructions for microsoft/generative-ai-for-beginners, covering agents.md, project overview, setup commands, initial repository setup and clone the repository.