FAQ
1. Where is the extension's database stored?
For versions 1.7.0 and newer (OPFS):
I originally thought the database was stored inside of binary files managed by Chrome, but that appears to not be the case. I was able to locate my HTU database using Chrome on Linux by following the steps below. (I assume these same steps can be used on other operating systems and Chromium-based browsers, but I do not know that for sure.)
Visit the "chrome://version" URL and take note of your "Profile Path".
Open HTU, which will sync your history, thus updating the database. Take note of your computer's current time. Also take note of your "Database Size" on the Options page.
Close Chrome.
Go to the directory indicated by your "Profile Path" in the first step. Then open the "File System" directory.
There will be a lot of subdirectories whose names are 3-digit numbers (e.g., "001"). Your HTU database will be deep in one of those subdirectories. For example: "018/t/00/00000000", where "00000000" is the filename of the SQLite database. You will need to match up the timestamps and sizes of files with the time and database size you noted in the second step. While this might be tedious, it is at least possible to do. When you identify a file you suspect is your database, you can copy it, save it to a safe location, and try opening it in any SQLite-compatible program ("DB Browser for SQLite" is one example, of many). If it can be opened and contains tables called "urls" and "visits", then it is your HTU database.
For versions 1.6.2 and earlier (WebSQL):
The database is located in a subfolder in your Chrome profile directory. To find your Chrome profile directory, go to the "chrome://version/" URL and look for "Profile Path". Go to that directory, and then open the "databases" folder, followed by the "chrome-extension_pnmchffiealhkdloeffcdnbgdnedheme_0" folder. The database will be there. The name of the file is a number (e.g., "16"); the contents of the file is a SQLite database.
2. Does history sync automatically? If so, how often?
Yes, history is synced automatically. It happens each time Chrome starts up, as well as when you open the "Trends" or "Search" pages in the extension.
3. How do I remove all data from the extension?
The quickest and easiest way is to uninstall the extension.
4. Does this extension preserve the purple color of previously clicked links?
No. The extension stores its data separately from Chrome's history, so it will not preserve the color of visited links.
5. Will this extension preserve history during Incognito mode?
No. The extension uses Chrome's History API, which means only URLs that appear in Chrome's history will be preserved.
6. Is there a way to import my Firefox history into this extension?
Yes, instructions can be found on the Import Firefox History page.
7. Will you make a version of the extension for Firefox?
Yes, once it is possible to do so. Keep an eye on Firefox issue 1673477. Once it is fixed, I should be able to port this extension to Firefox. And please see FAQ #11: The extension is closed source, so forks are not allowed.
In the meantime, you can use the instructions here to periodically export your Firefox history into a file that can be imported into HTU once the Firefox version is ready.
8. Will history synced from other devices appear in the extension?
Yes. Historically, extensions were only allowed to see history from the local device. However, in summer 2023 Chrome made a change so that extensions can see synced history. The announcement is here.
9. Will you add support for saving backups to the cloud?
I don't have any plans to do so. I think it could introduce privacy and security issues that I don't want to deal with. However, you may be able to choose a custom directory on your computer in which to save backups. You could then link that directory to a cloud storage provider. See FAQ #15 for details.
10. Does the extension work on the Chromium-based Microsoft Edge browser?
Yes.
11. Is the extension open source?
No, it is closed source. Copyright 2013-2024 Randy Lauen. All Rights Reserved.
12. Why do I sometimes get a SQLITE_BUSY error saying the "database is locked"?
This began happening in 2023 after migrating to the new storage system (SQLite Wasm using OPFS). It occurs when trying to use the extension immediately after starting Chrome, while the extension's start-up process is running. (The start-up process is responsible for syncing history and downloading the auto-backup file.) Unfortunately, the new storage system has poor support for concurrent database access. The developers of the SQLite database say this:
"Work to improve concurrency support on OPFS-hosted databases is an ongoing process. As OPFS's locking support evolves, and more fine-grained control of locking becomes widely available, the sqlite3 VFS will take advantage of it to help improve concurrency." (source)
In the meantime, if you see the error, just wait a bit and try again.
13. Why did my history in HTU suddenly disappear?
The CCleaner program is known to delete the files containing HTU's database, incorrectly thinking they are temporary cached data. Uncheck the "Internet Cache" boxes within CCleaner and it should stop deleting your history.
It's also possible the Windows 11 Storage Sense feature has the same problem. In addition, one HTU user reports that WinToys was the cause of their disappearing history (using the Microsoft Edge browser), although they did not specify which feature of WinToys might have caused the issue. There are almost certainly other culprits, too.
See also the forum discussion at https://sqlite.org/forum/info/542fba6a46cec787.
14. Why do I keep getting errors like "database disk image is malformed"?
This began happening to some users in 2023 after migrating to the new storage system (SQLite Wasm using OPFS), and it means your database has become corrupted.
How to Recover
For 1.7.5 and later, the corruption alert on the Search page will allow you to delete your corrupted database and create a new one.
For 1.7.4 and older, the only way to recover a corrupted database is to reinstall the extension and import history from your .tsv backups.
Possible Causes of Corruption
Some users have reported that Chrome crashing or being force killed causes their database to become corrupt. Unfortunately, there's not much that can be done to prevent those cases.
Some users who encounter corrupted databases report that they rarely restart Chrome. The new storage system is much more sensitive to the state of the browser. It may be that Chrome needs to be restarted semi-regularly to avoid corruption. For what it's worth, I restart Chrome at least weekly, sometimes even daily, and have not encountered corruption on MacOS, Windows, or Linux (knock on wood).
While this has not been proven to cause corruption, you should avoid interrupting a running operaton in HTU, if possible. For example, when importing a file, don't close the tab or navigate to a new page in the same tab before the import is complete. This applies to any operation, such as loading, searching, exporting, etc.
There are almost certainly other causes of corruption that are as yet unidentified.
Additional Background
HTU isn't the only program with this problem; other developers using the new storage system have reported similar issues. Google (which makes Chrome) and the creators of the SQLite database are aware of the issue. One of the SQLite developers says this:
"So far we have no concrete insights into specific causes of corruption. Every test we've run and every bit of feedback we've gotten from others suggest that the primary causes of corruption are environment-specific factors (of which there are countless potential culprits)." (source)
Unfortunately, we just don't know the root cause. It could be anything from a 3rd party program you're running, to a defect in your computer's hard drive, to a bug in HTU, a bug in SQLite, or a bug in Chrome. Or it might be something else entirely.
If you are able to identify any pattern to the corruption, please let me know. My email address is shown in the Feedback section of the Options page in HTU.
15. Can the auto-backup file be saved somewhere other than the Downloads folder?
This is probably the #1 most requested feature. Historically, it wasn't possible to save it anywhere else. A few years ago, Chrome added a new File System API that made it possible to save to a custom folder, but there was one major problem: you had to grant access to the custom folder every. single. time. This would get very old very quickly. Chrome has recently (2024) added a way to store persistent permissions for the File System API so you only need to grant access to the custom folder once. I will investigate adding custom download folders to HTU soon. Stay tuned.