How Onhand and Sider differ
| Onhand | Sider | |
|---|---|---|
| Focus | Reading and learning on the page you have open | An all-in-one AI sidebar for search, reading and writing |
| Answers | Highlights the passages it used on the page, with notes in the margin | Answers in the sidebar; its store listing doesn't mention marking up the page |
| AI models | Onhand Free, your ChatGPT plan, or your own OpenAI, Anthropic, Google Gemini or OpenRouter key | Many models in one place, including GPT, Claude, Gemini, DeepSeek and Grok, with group chat to compare them; bring your own key |
| PDFs | Opens PDFs in its own viewer to highlight and annotate them | Chat with, summarize and translate PDFs |
| Learning | Learning mode: guiding questions, quizzes tied to the page, and a This session panel | Quick lookups that explain or translate words, and read-aloud |
| Price and code | Free tier with a daily limit, or your ChatGPT plan or own API key; open source | See Sider's website |
Sider details are from Sider's Chrome Web Store listing as of October 2026. Sider is a trademark of its owner; Onhand isn't affiliated with it.
Built for the page you're reading
- Answers you can check: every point is highlighted where it comes from, so you read the evidence instead of trusting a summary.
- Notes in the margin: a sentence or two beside each highlight, so you keep your place on the page.
- Citations followed: ask what a reference like [14] says, and Onhand opens the cited paper and answers from it.
- A tutor when you want one: Learning mode asks before it tells and quizzes you on the page.
When Sider fits better
Sider does much more outside reading: writing help in text boxes across sites, translating whole pages and PDFs, bilingual YouTube subtitles, AI answers alongside search engines, and comparing several models' answers side by side. If those are what you need most, Sider covers them; Onhand is focused on reading and learning.
Try it
Add Onhand to Chrome, open the page you're reading, and click the
Onhand icon or press Ctrl+Shift+Space
(⌘+Shift+Space on a Mac). Onhand Free needs no account
or API key and has a daily limit; you can also sign in with your
ChatGPT plan or use your own OpenAI, Anthropic, Google Gemini or
OpenRouter key.