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Create A Dark/Light Mode Switch with CSS Variables

Ananya Neogi on April 10, 2019

Giving your users a way to customise the interface to their preference is a huge win for user experience. Here we are going to provide the user wit...

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Ben Halpern • Apr 10 '19

Just how we do it with dev.to!

CSS variables are awesome.

Yashu Mittal • Apr 11 '19

Wait, what! There is dark theme for dev.to, nobody told me about that. 😂

Ben Halpern • Apr 11 '19

Dark mode is new, and it's fabulous (with a few kinks that still need to be worked out).

Yashu Mittal • Apr 12 '19

Oh! I see. How can I enable dark mode?

Ananya Neogi • Apr 12 '19

Settings ➡ Misc. On that page you'll find it under "Style Customization"

Yashu Mittal • Apr 14 '19

Awesome, thanks. Looks cool.

Ananya Neogi • Apr 11 '19

Love the dark mode on dev.to! 🙂

gevv • Oct 15 '20

@Ananya Neogi

Hi,

Dark mode does not not work link open new window (target="_blank" links)

is there a solution?

Thanks
Best regards

Zonayed Ahmed • Jun 17 '19

Where is bro? Just tell me where is it? I didn't know about it...

MrCaspan • Feb 10 '20 • Edited

Hey just found a simple error in your CSS

.theme-switch-wrapper {
display: flex;
align-items: center;

em {
margin-left: 10px;
font-size: 1rem;
}
}

You have a nested selector here, this does not work in CSS only SCSS

so to fix it I just broke out the one selector to be on its own and not nested one!

.theme-switch-wrapper {
display: flex;
align-items: center;
}

.theme-switch-wrapper em {
margin-left: 10px;
font-size: 1rem;
}

Thomas Steiner • Aug 9 '19

CSS variables are fantastic for use cases like this. Here's a <dark-mode-toggle> that initially respects prefers-color-scheme and allows for manual overrides. Read more about it in this article.

Félix Paradis • Jun 7 '20 • Edited

Just added mine over at felixparadis.com :)

Quick note about accessibility though:
If you just display:none; your input, you're making it unaccessible through keyboard navigation.
Just hide it behind the label instead and everyone can toggle 🎉
Then add aria-label="Switch visual theme" to your input and blind users can know what's it about.

Bhupesh Varshney 👾 • Apr 11 '19

Nice post 👌👌 🤩
Gonna embed into my portfolio

Liz Jewell • Apr 13 '19

Thanks for this! I haven't tried my own light/dark mode since I tried implementing it on my first bootcamp project a couple years ago. I technically got it to work, but the code was not this DRY as I made two individual buttons that would add/remove a "dark" or "light" class on the entire body element. 😂 Your solution is much better!

Ananya Neogi • Apr 11 '19

Yes, this makes more sense. Thanks! 🙂
I'll update the demo.

Null • Sep 22 '19

this doesn't work for me. console says 'toggleSwitch is null'

Suryakumar Arumugam • Apr 29 '20

Add the JS inside DOMContentLoaded method

MrCaspan • Feb 10 '20

add the code after the switch in tags

Kiberu-sys • Jul 23 '20

Thanks for this great post Ananya. I followed the instructions and managed to get the page up and running. But i am getting a console log Error: script5007 unable to get property 'addEventListener' for undefined or null source. Could someone please help me with a solution. Thanks.

Simon Coudeville • May 7 '19

Very cool.

Have you thought about the prefers-color-scheme media feature? How could this be implemented in this script? You should check that too In my opinion. The toggle would have to automatically switch to the preferred color scheme.

Roland Taylor • May 21 '19 • Edited

I'm planning to experiment with something like this, but using CSS only (no javascript).

Zahir Stewart-Eaton • Oct 8 '19

I keep trying to serve it via ng serve but instead i get the error "Property 'checked' does not exist on type 'Element" referring to "if (currentTheme) {
document.documentElement.setAttribute('data-theme', currentTheme);

if (currentTheme === 'dark') {
    toggleSwitch.checked = true;
}

rugk • May 21 '19

You won't believe it, but actually you can nowadays even take the operation system setting for the dark mode and apply/get that, so your users don't even need that toggle, or at least use the version they prefer, by default.
With CSS and JS…

DeschainX 𓅓 • May 4 '20

In my case, I would offer two toggle for users which are auto mode (system dark mode) and manual Light/Dark toggle, so users can choose whatever they prefer.

Matthew • May 25 '21 • Edited

Amazing work

Eray#6421 • Sep 9 '19

How we can set this for all pages?

Desi • Apr 14 '19

this is great and so helpful - thanks so much! I do have one question - in the js, where does "light" come from? unless I'm missing it, that's not defined in the CSS, is it?

Ananya Neogi • Apr 15 '19

Hi Desi!
You're right, it's not defined anywhere.
If CSS doesn't find any specific styles related to light it will default back to the normal variables defined in :root.

Why I added it?
I added it so that we can use it while checking for the saved theme in localStorage further and add it to the root element. It will also be useful in cases where you might want to add some specific styles for light apart from the default styles.

I hope this helps 🙂

Desi • Apr 15 '19

Awesome, thanks so much! Explanation makes perfect sense.

Ananya Neogi • Apr 15 '19

You're welcome 🙂

Jan Wedel • Apr 11 '19

Great post. I would love to add a Dark theme to my website, but probably won’t have the time 😭. Bookmarked your article anyways 🤓

Sagar • Apr 13 '19

Super duper thanks for article.

Lucas Bittencourt • Apr 10 '19

Thanks! It will help me a lot. I've been using it wrong (but working), now you've cleared my mind. :)

rhymes • Apr 11 '19

Thank you Ananya! Great article, loved the tip about how to come up with a night theme :)

Charles • Feb 8 '20

Thank you for taking the time to write this article, it has been a great help! Would you follow this for all types of run time theming too, or do you think there is a better way to have multiple themes which people can switch between?

MrSid • Sep 10 '20

I visited your website and just loved it.
Could you help me with websites like this please.
Which language have you used for Backend? Could you make a tutorial for a simple blog website please.