What I Learned Building My First Chrome Extension for Google Calendar

James Brown — Thu, 28 May 2026 17:32:05 +0000

Recently I launched my first Chrome extension: Tint Calendar, a small tool that adds more color options and text color customization to Google Calendar.

The idea was simple.

I use Google Calendar a lot, and at some point the default color options started to feel too limited. I wanted more control over event colors, better readability, and a more flexible way to visually organize my calendar.

So I decided to build a browser extension.

At first, it looked like a small side project.

In reality, it taught me much more than I expected: about browser extensions, Manifest V3, DOM integration, permissions, Chrome Web Store publishing, product positioning, SEO, and the painful truth that building the product is only half of the work.

Here are the main lessons I learned.

1. Browser extensions are small products, not just small scripts

Before building the extension, I thought of it mostly as “some JavaScript running on a page.”

Technically, that is partly true.

But once you want to publish it and give it to real users, it becomes a product.

You have to think about:

permissions,
browser compatibility,
user trust,
privacy,
store screenshots,
onboarding,
edge cases,
updates,
product description,
SEO,
support.

That was probably my first real lesson.

A Chrome extension may be small in code size, but it still needs product thinking.

2. Manifest V3 changes how you think about extension architecture

Chrome extensions now use Manifest V3, and that affects how you structure the project.

You usually work with things like:

manifest.json,
content scripts,
service workers,
browser storage,
host permissions,
extension permissions.

For my case, the most important part was the content script, because Tint Calendar needs to interact with the Google Calendar page itself.

A simplified structure looks like this:

{
  "manifest_version": 3,
  "name": "Tint Calendar",
  "version": "1.0.0",
  "permissions": ["storage"],
  "host_permissions": ["https://calendar.google.com/*"],
  "content_scripts": [
    {
      "matches": ["https://calendar.google.com/*"],
      "js": ["content.js"]
    }
  ]
}

Of course, the real extension has more details, but this gives the basic idea.

Manifest V3 also makes you think more carefully about what should run in a content script and what should live in the extension background/service worker layer.

3. Working with someone else’s UI is fragile

This was one of the most important lessons.

Google Calendar is not my application. I do not control its DOM, CSS classes, layout, updates, or internal structure.

That means any extension that integrates with it has to be careful.

If Google changes something in the UI, the extension may break.

This is very different from building a normal web app where you own the markup and components.

When working with an external app UI, you have to think defensively:

avoid relying too much on unstable class names,
observe UI changes carefully,
handle missing elements,
avoid breaking the original page behavior,
make the extension fail gracefully.

This is the kind of work that looks simple until you actually have to make it reliable.

4. Permissions matter a lot

When you build a Chrome extension, permissions are not just a technical detail.

They are part of user trust.

If your extension asks for too much access, users may not install it. And honestly, they probably should not.

For Tint Calendar, I wanted to keep the permission model as small as possible.

The extension needs access to Google Calendar pages because that is where it works. It also uses browser storage to save user color preferences.

That is it.

No extra account.
No server-side calendar data.
No unnecessary tracking.

This became an important product decision, not just a technical one.

5. Local storage is simple and good enough for an MVP

For the first version, I did not want to build accounts, cloud sync, or backend infrastructure.

So I used browser storage for saving preferences.

For a small utility extension, this is a good starting point.

It keeps the product lightweight and reduces complexity.

The tradeoff is that data may not sync across browsers/devices unless you specifically build that behavior. But for an MVP, simplicity is often the right choice.

A product does not need a backend just because developers like building backends.

And yes, I am saying this as a backend developer.

6. Chrome Web Store publishing is a product exercise

Publishing to the Chrome Web Store is not just uploading a zip file.

You need to prepare:

extension name,
short description,
full description,
screenshots,
promotional images,
privacy policy,
permission justifications,
category,
support email,
store listing copy.

This part took more thinking than I expected.

You need to explain the product clearly and honestly.

What does it do?
Who is it for?
Why should someone trust it?
Why does it need these permissions?

If the product is small, the explanation should be even clearer.

7. Screenshots are more important than you think

For a visual extension, screenshots matter a lot.

People do not want to read a long description first. They want to see what changes.

For Tint Calendar, the key visual message is:

before: limited default Google Calendar colors,
after: more event colors and text color customization.

That sounds obvious, but it took me a while to realize that screenshots are not just decoration.

They are part of the conversion funnel.

A good screenshot should answer the question:

“What will this extension do for me?”

8. Building is easier than distribution

This was probably the biggest lesson.

Building the extension was fun.

Getting people to discover it is much harder.

After publishing, I quickly realized that the Chrome Web Store does not magically bring users. You still need distribution.

That means:

SEO,
articles,
directories,
Reddit discussions,
Product Hunt,
YouTube demos,
backlinks,
reviews,
community feedback.

I wrote a guide about changing colors in Google Calendar because that is what people actually search for.

Most users do not search for your product name.

They search for their problem.

For example:

“how to change colors on Google Calendar”
“how to add more colors to Google Calendar”
“Google Calendar custom colors”
“Google Calendar text color”

That changed how I thought about marketing.

The product should meet the user at the problem, not expect the user to know the product already.

9. Naming and positioning are hard

I started with the name Tint Calendar because I liked the idea of adding color and visual clarity.

But then I had to think about search intent.

People do not search for “Tint Calendar” yet.

They search for “more colors for Google Calendar.”

So the positioning became something like:

Tint Calendar — More Colors for Google Calendar

This combines the brand with the actual user problem.

That was another important lesson: a product name can be nice, but the positioning must be obvious.

Especially for a small extension.

10. Small products still need support and maintenance

Even if the extension is simple, it still needs maintenance.

Google Calendar can change.
Chrome extension policies can change.
Users may report bugs.
Screenshots may become outdated.
Privacy declarations may need updates.
SEO pages need improvement.

A small product does not mean zero maintenance.

It just means the maintenance surface is smaller.

11. What I would do differently next time

If I were starting again, I would do a few things earlier:

write the landing page before publishing,
prepare SEO articles earlier,
create better screenshots from the beginning,
think about Chrome Web Store keywords sooner,
collect feedback before launch,
make a small demo video earlier,
prepare a list of directories and communities in advance.

The biggest change: I would not treat launch as the finish line.

Launch is just the moment when the real work starts.

Final thoughts

Building my first Chrome extension was a great learning experience.

It looked like a small technical project, but it quickly became a lesson in product thinking, user trust, distribution, and positioning.

Tint Calendar is still a small extension, but that is exactly what made it useful to build.

Small products are great teachers.

They force you to make decisions, ship something real, and face the uncomfortable question:

“Okay, it works. Now how will people find it?”

That question is where software development starts turning into product building.

And honestly, that is where it gets interesting.

I also wrote a full user guide here: link

And the extension is here: link

DEV Community: James Brown