Intel / article

Introducing Authenticated Fetch

Source: browserbase.com
Author: Browserbase
Date: Published Oct 27, 2026

Context

Browserbase's Fetch API, which returns a page's content without starting a browser session, can now read pages behind a login. Authenticated Fetch reuses a login an has already completed in a Browserbase browser. The cookies from that login are stored in a , Browserbase's saved browser state carried between sessions, and a Fetch request that includes the Context's ID sends those cookies with the URL. An agent that has signed in to a supplier portal can then check an order-history page repeatedly without opening a browser for each check. The response can still be raw content, Markdown, or JSON fields that a extracts according to a schema the developer supplies.

The shortcut covers reading, not signing in. The login still happens in a browser session started with persistence turned on, and its cookies are saved only when that session ends. Fetch reads the saved cookies but never writes changes back, so when a site's login expires the agent has to return to a browser, sign in again and end that session to save the new state. Browserbase's example switches later checks to Fetch only if the portal serves that page's content without JavaScript rendering, and Contexts last saved before September 1, 2026 need one fresh persisted browser session before Fetch can use them. Browserbase says the feature carries no additional cost on any plan.

Key takeaways · AI-distilled

Setup takes three steps: create a Context and start a browser session with persist: true, log in and end that session so its cookies are saved, then send the page URL and the contextId to Fetch.
Browserbase positions cookie reuse for pages served without JavaScript rendering. Its example is a supplier portal's order history page, checked repeatedly with Fetch after a single browser login.
Fetch reads cookies from the Context's last saved browser session, follows browser-style domain and path rules (including across redirects), drops expired cookies, and never writes cookie changes back to the Context.
When a site's login expires, you refresh it with another persist: true browser session. Contexts last saved before September 1, 2026 need one such session before Fetch can use them.
Authenticated requests work with Fetch's raw, markdown and schema-based JSON outputs. JSON extraction uses a language model, so Browserbase advises checking the result before the next step. The feature costs nothing extra on any plan.

Terms in this piece · Glossary

AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
context window — The maximum amount of text a model can consider at once — its working memory for the current conversation or task.
LLM — A large language model — the neural network behind tools like Claude and ChatGPT, trained on huge amounts of text to predict what comes next.

Read the source browserbase.com