Chrome extensions, Manifest v3 and local storage views

The other day I started coding a Chrome extension that makes heavy use of Chrome’s IndexedDB. Until this time then I had no problem inpecting any local storage using the DevTool’s “Application” tab. Those were extensions that used Manifest v2 but as of June 2023 Google will only acept Manifest v3 extensions.
One of the main changes is that background pages are replaced with service workers. So I changed my code accordingly from:

"background": {
    "page": "background/background.html"


"background": {
	"service_worker": "background.js",

and coded happily on. When I reached the local storage part and wanted to check the local storage by clicking on the new “service worker” link:

Surprisingly the IndexedDB pane in the “Application” tab was empty though I definitely knew that there was data stored:

So what was happening? After a long search on the Internets I came across an answer on StackOverflow that saved my day.

If your extension contains a popup you can right click and select “Inspect” to open the correct DevTools window:

And there you go:

But what do you do if your extension does not containa popup? There is a solution though it’s a bit more complicated.
Open the extension page and look for the extension’s ID:

Copy that ID and enter the following URL into the address bar, replacing “ID” with the actual ID:


Right click on the window and select “Inspect”:

One last problem: In contrast to the standard DevTools popup this one disappears if you reload the extension. Fortunately you can bookmark the tab:

Update: You don’t actullay need to insert the ID manually but you can click on any script in your default Devtools window (opened with “Inspect views service worker” link), right click on any script in the “Sources” pane, select “Open in new tab” and, just like above, right click the tab and select “Inspect”:

The only question that remains is: Why, Google, why has this be so complicated?

How-to split a number into equal chunks

The other day I had to iterate over a large number of items but to avoid a timeout I could only compute a certain amount at a time. So I had to split the number into equal chunks and a remainder. Here’s an easy way to determine the chunk size:

$totalNumber = 50321;
$chunkSize = 1023;

$remainder =  $totalNumber % $chunkSize;
$chunks = ($totalNumber - $remainder) / $chunkSize;

The code return the following values:
$remainder => 194
$chunks => 49

Verification: (49 * 1023) + 194 = 50321

How does it work?
In line 4 $totalNumber is divided by a modulo operator (“%” is the PHP token for modulo). The operator returns the remainder of the division (194 in this case). By subtracting this value from $totalNumber it becomes a whole number multiple of $chunks and the division with $chunkSize equals the desired number of $chunks (line 6).
Now you have the number of necessary iterations and the remaining part.

Big Tech 0wns web development

Web development is based on free software by developers like you and me, isn’t it? At first glance, this seems to be the case. Let’s take a look at the main tools modern web is mainly developed with nowadays:

  1. Visual Studio Code
  2. TypeScript
  3. React
  4. npm
  5. GitHub
  6. Chrome

Most of the tools are Open Source projects (VS Code only in parts, npm is proprietary). So where are the big companies? Well, all six tools and sites are owned by Big Tech:

  1. Microsoft
  2. Microsoft
  3. Facebook
  4. Microsoft
  5. Microsoft
  6. Google

The tools we use all day rise and fall with the benevolence of companies typically seen as enemies of Free Software by the majority of Open Source developers.

Especially GitHub and npm are irreplaceable because of their large data collection. If Microsoft decides to pull the plug from one moment to the next, the access to the vast collection of free code will be gone at least for some time and the build processes of millions of programs will break.

Of course, these services can and would be replaced by others, but it would take some time until dominant services will emerge and web developers would need to find an interim way of accessing their externalized source code.

(Photo by Max Bender on Unsplash)

WordPress: add_filter or add_action? It actually doesn’t matter!

It’s a doctrine of WordPress plugin development:

Use actions to expand the functionality and filters to change information.

We’ve all heard it, we always follow that demand. Always? Well…

… if I want to add some functionality and nowhere near or far there is an action hook in the core but only a filter hook, I use that hook without considering the doctrine.

Surprisingly it works. But why? If we all insist that you have to use the right hook type, there has to be a difference between them. Let’s take a look behind the scenes (/wp-includes/plugin.php):

function add_action($tag, $function_to_add, $priority = 10, $accepted_args = 1) {
   return add_filter($tag, $function_to_add, $priority, $accepted_args);

What? add_action does nothing but call add_filter and nothing else? There is no difference in functionality, it’s only a different name. So there is no reason why you shouldn’t use add_filter instead of add_action if you have no other solution.

I don’t say that you should interchange filter and action hooks at will. Using the correct hook type makes your code more readable and maintainable, for yourself and for others. Nevertheless, if there’s not other way to accomplish your goal but to use a filter hook instead of an action, don’t hesitate, it virtually makes no difference.

Firefox Add-On version hack: Cutomize titlebar

If I want to tweet a link of a site currently opened in my Firefox/Waterfox browser I using the “Hootlet” from “Hootsuite“. This little Add-On simply takes the text  of the titlebar of the browser and adds an link so I can tweet it with a single click.

Unfortunately Firefox adds “Firefox” to the titlebar which I have to delete manually every time. But hey, computers are for automationing things so this should be automated, too. The Add-On repository contains an Add-Ons called “Customize Titlebar” which would do exact the requested task but it hasn’t been updated 2009 and is compatible with Firefox 3.9 (!).

In many cases those Add-Ons still work with current versions of Firefox the only problem is that they are marked incompatible. It’s always worth a try to simply increase the entry and check if it still works. Especially Add-Ons that are not critical like “Customize titlebar“. In this case this little hack actually works and I’m happy to be able to use the plugin.

I set the compatibility information of the Add-On to “50.*” so it should work for some while.


First meeting for launching a hackerspace in Kassel/Germany

Kassel, a city located at the Fulda, population 200,000, is as ugly as sin but it’s got the <a href="Herkules, a pile of museums, a great hackerspace, a national theatre, a university

Wait, wait, wait! A hackerspace? In Kassel? No, of course there isn’t one. Not yet. But there could be soon. Some people thought they could change this state and create such a space in Kassel, whereby space does not exclusively has to be taken as a physical room.

So the call went out into the great wide open of the Internet and the initiators hoped for a small group of interested people. at the first meeting in a small pub this small group turned out to be a large group of 28 combatants.

Unfortunately the locality was quite unsuitable for such a large group. If only five or ten people had shown up it would have been a nice and cosy get-together but actually we had to make the best of the circumstances. Some verbal contributions could hardly be heard others not at all. But nobody could expect such an immense interest. Nonetheless everybody was concentrated and the discussion was quite constructive. After a short introduction to the basic ideas of hackerspaces everyone told a bit about his background, his intentions, ideas, and expectations. I think a lot of Blinkenlights will be created in the near future.

Obviously there is a great crowd of hardware freaks, programmers, and artistically interested men (yes, there wasn’t a single woman) having many ideas for new and/or interesting projects  and ideas how they can help others and how others can help them. The initiators presented a welled planned  concept and even looked after some affordable rooms with a good infrastructure. Next week we will have a go and see.

Hopefully everybody will keep at it and the new hackerspace will have a good substantial and financial foundation. It’s going to be interesting!