Your library
Save, read, highlight, and search in the browser.
Open your librarySave, read, and research with your sources
Save articles and PDFs in a private library. Read, highlight, and make notes. Use your own agent to investigate the sources and develop your research.
Ask your own agent: Find coral bleaching field studies with measurements. Save the ones you want to read.
Sign in with your Sponge account, or create a new one. Your library starts private. Saving an article does not publish it.
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Save articles and files for later. Open a saved copy to read, highlight a passage, or add a note.
Sponge interface · fictional notes and sources · Read the guide
- Save
- Keep articles and PDFs with a retained copy of the source.
- Read
- Highlight a passage, add your own note, and return to where you left off.
- Research
- Use your own agent to analyze a source, check its references, and develop your findings in a document.
Read the source, keep your own notes
The article, your notes, and saved answers each have their own place.
- A copy you can return to
- Read the saved text and download the retained source. Later copies keep their own date; existing highlights stay with the version you read.
- Your words beside the source
- Highlight across paragraphs and keep a note with the passage. Your notes remain separate from saved summaries and answers.
- Research you can check
- Give selected passages to your own agent. Ask it to cite the passages it uses, check its claims against the saved text, and keep gaps in coverage visible.
From your reading to your research
Start with one article. Bring your own agent when you want to investigate further.
Save a link or file
Add an article or PDF to your library. You do not need to create a document.
Read and make notes
Keep useful passages, add your thoughts, and mark an item as read when you’re finished.
Develop the research
Use your own agent to ask questions about saved sources or write a document. You choose when to share your work.
Read, write, or use your own tools
Your library and documents are available in the browser and through the API.
Your research
Write with your own agent, inspect sources and changes, and invite collaborators when you want to work together.
Open documentsYour own tools
Use the API or CLI to save sources, read your library, export originals and notes, and work with documents.
Explore the APIYou decide what to keep and share
Your own agent can help investigate and draft. Reviewing its work does not publish it.
- Private by default
- Your saved copies, highlights, and notes are private. Sharing a document does not share your source archive.
- You choose what gets saved
- Save sources you want to keep in your Library. Highlights and notes stay with your private saved copy.
- Saved analysis stays readable
- Earlier overviews and answers remain available with their source references. They do not become accepted findings or public research without review.
Before you begin.
What can I save?
Public web articles, PDFs, and supported text files. Sponge keeps the acquired file or page separately from the readable copy. If it could save only part of the text, the reader says so.
How do I develop research?
Save sources in Library, then use your own agent to analyze selected passages and write in a document. Local monitoring is planned but is not available in Sponge yet.
What does my own agent add?
Use Codex, Claude Code, or another agent you choose to investigate sources and draft documents through Sponge’s tools. Built-in hosted analysis is retired; saved answers and overviews remain readable.
Will saving a long paper create hundreds of findings?
No. Saving a source does not start hosted analysis or extract findings. Use your own agent when you want a summary or more detail. Earlier saved results remain readable.
Can I take my library with me?
Yes. Download a saved original from the reader. The API and CLI also export retained copies, highlights, and notes.
Is my library public?
No. Your library is private. You can share an authored document or publish a version of it without publishing your private source archive.
Do I need an account?
Yes. Sign in with your Sponge account, or create one, to save articles and keep your reading across devices.
Who makes Sponge?
Ben Guo, a musician and builder who was previously a founder and engineering leader at companies including Venmo and Stripe. He builds Sponge from Puerto Rico under Hraness.
Ben Guo
Sponge is built by Ben Guo, a musician and builder, formerly a founder and engineering leader at companies including Venmo and Stripe, now building from Puerto Rico. Sponge brings writing, source material, and agent research into one workspace.
Begin in private
Save something you want to read.
Add an article or PDF to your library. Read it now, or return when you have time.
Sign in with your Sponge account, or create a new one. Your library starts private. Saving an article does not publish it.