800 Links in My Bookmarks, Fewer Than 20 I Actually Open

The conclusion first: the value of a "treasure site" isn't novelty, it's revisits. The test is simple — will you still open it for the 20th time six months from now? Filtered by that standard, fewer than 20 of my 800+ bookmarks survive, and these 15 are the ones in steady use. All free, no registration.

1. Checking whether something is true, and where it came from

• Wayback Machine — web.archive.org. Web archaeology. Articles get deleted, official sites get redesigned, but the historical versions are still there; it's the fastest way to see "how it was originally written."
• Our World in Data — ourworldindata.org. Global public data, every chart downloadable, every number sourced. Cuts report writing time in half.
• Chinese Text Project — ctext.org. Full-text search of classical Chinese texts with Chinese-English side by side; more accurate than a search engine for tracing a line of classical prose.
• Shuge — shuge.org. High-resolution scans of classical books, public domain, directly downloadable.

My criterion for this group is "has a primary source": you can click back to the origin from the page, rather than a secondhand retelling.

2. When you need to make something quickly without installing software

• Photopea — photopea.com. Photoshop in the browser, opens PSD files directly, and the free tier is enough for everyday image edits.
• Excalidraw — excalidraw.com. Hand-drawn-style whiteboard; far faster than PowerPoint for flowcharts and architecture diagrams.
• Squoosh — squoosh.app. Image compression that runs entirely in the local browser; images are never uploaded.
• PDF24 — tools.pdf24.org. Merge, split, compress, OCR — it has them all, with a Chinese interface and no registration.

This group has one criterion: does the file get uploaded? Local processing is a hard requirement, especially for contracts, IDs, and internal documents.

3. When you want to learn something without spending money

• Learn X in Y Minutes — learnxinyminutes.com. Explains an entire language in one block of commented code; my first stop when picking up a new language in a hurry.
• Explorable Explanations — explorabl.es. Interactive science explainers where you can drag parameters and run simulations; sticks in memory better than reading articles.
• PhET — phet.colorado.edu. Physics and chemistry lab simulations, good both for playing with yourself and for showing your kids.

4. Pure stress relief

• Radio Garden — radio.garden. Spin the globe and listen to the station of whichever city you land on.
• Window Swap — window-swap.com. Look out of strangers' windows around the world.
• Neal.fun — neal.fun. All kinds of odd little experiments, like "what would you see if you kept digging down."

Appendix: three I built myself

Since I started building sites, I've become extra careful about "recommendations," so a disclosure first: the three below are mine — free, no registration, no data collection. Click only if useful.

• tools.cosmocat.dev: 9 open-source apps turned into online versions (spreadsheets, UI design, vector drawing, video editing, PDF); open and use, files never uploaded.
• games.cosmocat.dev: 8 open-source games playable online, no download, no registration, each with 3 Chinese-language guides.
• craft.cosmocat.dev: a Chinese-language directory of 13 free open-source alternatives to Adobe / Office.

One last honest word

Bookmarking isn't using. Pick one from above and actually use it once today — that beats saving 100 links.

I also posted this answer to Zhihu: What treasure websites are worth recommending?