# Cairo Storage Mappings

> Explain Starknet storage mappings with Map, hashing of keys, and read/write patterns; use when a request involves mapping-like storage in Cairo.

- Skill: `teddyjfpender/cairo-storage-mappings` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add teddyjfpender/cairo-storage-mappings`
- Raw SKILL.md: https://api.skillmd.com/api/skills/teddyjfpender/cairo-storage-mappings/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: teddyjfpender (https://skillmd.com/u/teddyjfpender)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/teddyjfpender/cairo-storage-mappings

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# Cairo Storage Mappings

## Overview
Guide use of storage mappings, key hashing, and constraints around Map types.

## Quick Use
- Read `references/storage-mappings.md` before answering.
- Use `Map<key, value>` only in storage structs.
- Access with `.read(key)` and `.write(key, value)`.

## Response Checklist
- Remind that Map types cannot be instantiated as regular variables.
- Note that mappings are not iterable and return default values for missing keys.
- Mention that key hashing chains through multiple keys when needed.

## Example Requests
- "How do I store balances by address in storage?"
- "Can I iterate over a storage mapping?"
- "How does Starknet hash mapping keys?"