extension

basicwidespread

A plugin is a small add-on program that gives an existing software – browser, editor, or AI assistant – new capabilities without replacing it.

In plain terms

An extension is like a changeable attachment for a kitchen food processor: the machine remains the same, but depending on the attachment, it whips cream, grinds, or kneads dough. Your browser, email client, or AI assistant can similarly gain new capabilities with a few clicks from an added extension.

In the AI world, you will encounter two types of extensions. One brings AI to where you work: for example, a browser extension that summarizes the open page or helps write an email. The other connects the AI assistant with other services: your calendar, your files, your correspondence.

This matters because extensions do a lot to turn a conversational chatbot into a tool that acts. On its own, the assistant mainly answers and at most uses its built-in tools (such as web search). With an extension, the agent can read, click and fill in forms on your behalf, right where you are working.

It differs from a standalone application in that it does not operate on its own: it always builds on a host program and works according to its rules and permissions.

How it works

The host program (for example, a browser) pre-defines connection points: it specifies what an extension can access and what it cannot.
You install the extension from an official store or the service's settings, usually with a single click.
During installation or first use, extensions request permissions, such as reading the content of open pages or accessing your calendar; you must approve these.
During use, the extension activates when you click on it or when you open a page for which it has permission. If needed, it sends the necessary content to an AI model, then displays or executes the result.
In extensions controlling AI agents, the model makes decisions step by step, while the extension executes clicks or typing; ideally, it asks you before sensitive actions.

An everyday example

You read a long English article in your browser and click a small icon next to the address bar in the browser toolbar to request a Hungarian summary. Behind the icon, an AI extension works: it reads the page text, sends it to the model, and outputs the essence within seconds.

Who is affected

everyoneMany people first encounter AI integrated into their usual programs through browser extensions.

employeeAn extension installed on a company computer can access internal documents and customer data, so many workplaces allow only approved extensions. → Work & HR

developerThe coding agent often arrives as a code editor extension (but versions running as command-line or standalone programs also exist), and it can itself be extended with additional tools. → Code

entrepreneur, executiveThe company must decide which extensions to allow, as these can cheaply increase efficiency but also bring data leakage risks.

A common misconception

MythIf an extension is on the official store, it is definitely reliable.

In realityStores filter, but data-collecting or malicious extensions regularly slip through, and an extension that was previously harmless can change with an update or a change of ownership.

Limits and risks

A browser extension sees only what permissions you grant: if it can read all websites, it can also access your online banking and webmail opened in the browser.
The AI extension often sends processed content to an external server, so only provide confidential text if you know where it will go.
An agent reading a website can also be instructed by hidden text on a page (prompt injection), causing it to do something you did not request.
Many extensions can slow down the host program, and unused, forgotten parts pose unnecessary risks – it is sometimes worth cleaning them out.

Similar, but not the same

Application – The application runs independently, while the extension functions only as part of another program.
konnektor – A connector specifically links data from an external service into an AI assistant, while an extension is broader: it can add any new function.
API – An API is a technical connector between programs used by developers; an extension is a ready-to-install product that often calls APIs in the background.

Related concepts

Broader

szoftver

Narrower

browser extension

On the edge

plugin, konnektor, MCP, tool use, prompt injection, AI assistant, AI browser, coding agent

A brief history

Extensions became mainstream with web browsers: the 2004 release of Firefox was already customizable with add-ons. The idea spread among AI assistants in 2023, when OpenAI announced ChatGPT plugins in March. These were discontinued in spring 2024, replaced by custom GPTs, then connectors and embedded applications. The common standard for linking assistants and external tools is MCP, published by Anthropic in November 2024.

Where things stand

At the end of 2026, most major AI assistants are available in the browser and in office programs – as extensions or built in – and the assistants themselves can be extended with external tools. Agent extensions that operate the browser autonomously and AI browsers are developing the fastest, but their security is not yet solved, mainly because of prompt injection.

Status: 2026 November

In the news

Appears in 20 Agent Age stories; the curve shows weekly occurrence in the news magazine.

DeepSeek's agent platform reaches 1.54 million daily users as Chinese open models spreadNov 2, 2026 · Agent Age
Universities set AI policies: Colorado, Nebraska, UIC and Harvard ExtensionNov 2, 2026 · Education & Family
Malicious Claude Code extension in Cursor marketplace reportedly reaches 5,000 usersNov 2, 2026 · Code
Tampered Claude Code extension installed an SSH backdoor on about 5,000 machinesOct 30, 2026 · Agent Age
Trojanized Claude Code extension on Cursor marketplace delivered SSH backdoor to developer machinesOct 29, 2026 · Code
GitHub Copilot comes to Teams, and Azure DevOps to Microsoft CopilotOct 23, 2026 · Code
Stack Overflow for Agents triples signups after launching ChatGPT pluginOct 16, 2026 · Code
Copilot administration: model and MCP controls, server-side settings, organization billingOct 12, 2026 · Code

Also known as

extension · Add-on · browser extension · extension · browser extension · add-on · plugin · plug-in

Sources

Chrome for Developers: Extensions

This entry was machine-edited and has undergone machine expert review; the “In the news” section updates automatically from Agent Age stories.