chrome-ext-storage

chrome-ext-storage is a skill for Claude Code from RadOrigin-LLC/RAD-Claude-Skills. It costs 106 tokens per session (922 once invoked), scanned A, original, Apache-2.0.

A guide to storing data in Chrome extensions. It explains the browser's storage areas and IndexedDB, a built-in database for larger or more structured data, including their different lifetimes, limits, and uses.

In plain words
What is it for?
Use it when designing or reviewing extension data storage, choosing between storage.local, storage.sync, storage.session, managed storage, and IndexedDB, or implementing persistence.
Why use it?
It helps choose where extension settings, temporary state, cached data, synced preferences, or large datasets should be kept.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the rad-chrome-extension plugin — 9 skills, 1 agent shipped together

Good fit Use it when designing or reviewing extension data storage, choosing between storage.local, storage.sync, storage.session, managed storage, and IndexedDB, or implementing persistence.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/radorigin-llc/rad-claude-skills/chrome-ext-storage
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.

Any agent
npx skills add RadOrigin-LLC/RAD-Claude-Skills --skill chrome-ext-storage
Clone the repo
git clone --depth 1 https://github.com/RadOrigin-LLC/RAD-Claude-Skills

Made for: Claude Code.

Or install rad-chrome-extension, the plugin that ships this one along with the rest of its 9 skills, 1 agent.

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 chrome-ext-storage

README.md
[![agentmods](https://agentmods.dev/badge/skills/radorigin-llc/rad-claude-skills/chrome-ext-storage/github.svg)](https://agentmods.dev/skills/radorigin-llc/rad-claude-skills/chrome-ext-storage)
Your own site
<a href="https://agentmods.dev/skills/radorigin-llc/rad-claude-skills/chrome-ext-storage"><img src="https://agentmods.dev/badge/skills/radorigin-llc/rad-claude-skills/chrome-ext-storage/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 chrome-ext-storage

Your own site · 80×15
<a href="https://agentmods.dev/skills/radorigin-llc/rad-claude-skills/chrome-ext-storage"><img src="https://agentmods.dev/badge/skills/radorigin-llc/rad-claude-skills/chrome-ext-storage.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 106 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 922 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 $0.00106 $0.00922
Opus 5 $0.00053 $0.00461
Sonnet 5 $0.00021 $0.00184
Haiku 4.5 $0.00011 $0.00092

Measured 11d ago against content hash 4f46078db2e0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

chrome-ext-storage 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 11d 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.

archive/plugins/rad-chrome-extension/skills/chrome-ext-storage/SKILL.md · 99 lines

How it starts

The opening of the file, as written. The whole thing — 99 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Chrome Extension Storage

Chrome extensions have four storage areas plus IndexedDB. Each serves a different purpose with different lifecycles, quotas, and trade-offs. Choose based on data size, persistence needs, and cross-device requirements.

Storage Selection Guide

Mechanism Best For Capacity Lifecycle
storage.session Hot state, temporary variables 10 MB (in-memory) Clears on browser close
storage.local Device settings, cached data 10 MB (expandable) Persists until extension removed
storage.sync User preferences across devices 100 KB total Syncs across Chrome instances
storage.managed Enterprise-pushed config Read-only Set by IT admin policy
IndexedDB Large datasets, binary data ~80% disk Persists until extension removed

When to Use What

storage.session — In-memory state that must be fast but doesn't need to survive browser restart. Service worker volatile cache. Authentication tokens for the current session.

storage.local — Default choice for most extension data. Settings, cached API responses, user data that stays on one device. Use unlimitedStorage permission to remove the 10 MB cap.

storage.sync — Small user preferences that should follow the user across devices. Subject to strict quotas: 8 KB per item, 512 items max, 1,800 writes/hour.

IndexedDB — Large datasets, binary data (images, model weights, video metadata), or data requiring structured queries. No JSON serialization overhead (uses structured cloning). Can use ~80% of available disk.

Data That Must Never Be Stored

  • Passwords and credentials in storage.local or storage.sync — these are NOT encrypted. Use storage.session for temporary auth tokens (clears on browser close).
  • Non-serializable objectschrome.storage only accepts JSON-serializable types. No Date, Set, Map, RegExp, or class instances.

Write-Through Cache Pattern

Read the full file on GitHub · 99 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 11d ago First seen · 99 lines · 106 tokens per session scan A 4f46078db2e0

Subscribe to this mod's changes

chrome-ext-storage is a skill published in the GitHub repository RadOrigin-LLC/RAD-Claude-Skills (5 stars, last pushed 25d ago), licensed Apache-2.0. It adds 106 tokens to every session and 922 once invoked, about $0.0005 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 2026-08-31.

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