Three Days Debugging One Line of NaN ☕

If you use Dual Dictionary, it may look like it simply appeared one day. It did not. Here’s the tiny, very human three-day backstage story.

Day 1 — A 404 error.
I checked the server, passwords, and even wondered whether someone had broken in. The real cause? The dictionary files lived in a “dicts/” folder while the app was looking in the root folder. Like searching for Oxford on the shelf when it is still inside the box. One line fixed it.

Day 2 — The domain disappeared.
While cleaning up configuration, I accidentally deleted the DNS record connecting the domain to the server. Basically, I tidied the house and threw away the key.

Day 3 — “File wasn’t available on site.”
A friend reported that downloads had stopped working. I inspected the response byte by byte and found this header: “bytes NaN-NaN/40975963”. NaN means “not a number” — the server was telling the browser something as useful as “from byte I-don’t-know to I-don’t-know.” One incorrect calculation. One line.

Three days, three bugs, three tiny fixes. But they reminded me that when you build for a community, “it runs on my machine” is not enough. It needs to work correctly down to every byte.

Everything is smooth now. If you have not tried it yet, visit dualdictionary.netlify.app — it is free, offline-friendly, ad-free, and requires no sign-up.

What should I build next? Leave an idea below ☕