Niels Leenheer
@html5test.com
CTO of Salonhub. Creator of http://html5test.com, writes at http://nielsleenheer.com, team @FronteersConf, Google Developers Expert, Invite me to speak at your event.
I'm down one of the rabbit holes again. I *just* wanted to print receipts on a Star TSP100 printer.
Initial problem: unlike other printers, it does not support text, only graphics. And my receipt printing library only supports rendering to text based ESC/POS and StarPRNT...
Initial problem: unlike other printers, it does not support text, only graphics. And my receipt printing library only supports rendering to text based ESC/POS and StarPRNT...
September 13, 2026 at 8:50 AM
I'm down one of the rabbit holes again. I *just* wanted to print receipts on a Star TSP100 printer.
Initial problem: unlike other printers, it does not support text, only graphics. And my receipt printing library only supports rendering to text based ESC/POS and StarPRNT...
Initial problem: unlike other printers, it does not support text, only graphics. And my receipt printing library only supports rendering to text based ESC/POS and StarPRNT...
At the train station in Freiburg after a very lovely @smashingconf.com, waiting on the night train back home. Been lovely talking to all the other attendees, speakers and organisers. See you next year!
September 9, 2026 at 9:56 PM
At the train station in Freiburg after a very lovely @smashingconf.com, waiting on the night train back home. Been lovely talking to all the other attendees, speakers and organisers. See you next year!
Lovely venue for the @smashingconf.com Jam Session!
September 7, 2026 at 5:11 PM
Lovely venue for the @smashingconf.com Jam Session!
Hello Freiburg 👋🏻
Anybody know a good place to have some lunch and where I can work on my talk a bit for tonight?
Anybody know a good place to have some lunch and where I can work on my talk a bit for tonight?
September 7, 2026 at 10:37 AM
Hello Freiburg 👋🏻
Anybody know a good place to have some lunch and where I can work on my talk a bit for tonight?
Anybody know a good place to have some lunch and where I can work on my talk a bit for tonight?
Over the years I have brought some really weird things through airport security. I’ve set off the alarms once - they closed down the lane and started shouting in panic because it looked really serious on the scanners.
But never a vintage oscilloscope. Until today. Freiburg, here we come!
But never a vintage oscilloscope. Until today. Freiburg, here we come!
September 7, 2026 at 4:52 AM
Over the years I have brought some really weird things through airport security. I’ve set off the alarms once - they closed down the lane and started shouting in panic because it looked really serious on the scanners.
But never a vintage oscilloscope. Until today. Freiburg, here we come!
But never a vintage oscilloscope. Until today. Freiburg, here we come!
Flying tomorrow to Freiburg for @smashingconf.com, now at my hotel at Schiphol editing slides for a small 10 minute Jam Session talk.
Was so swamped with work that I forgot to send @charismagic.studio what I wanted to talk about, so she just picked a title and I am now building slides to match 😅
Was so swamped with work that I forgot to send @charismagic.studio what I wanted to talk about, so she just picked a title and I am now building slides to match 😅
September 6, 2026 at 8:50 PM
Flying tomorrow to Freiburg for @smashingconf.com, now at my hotel at Schiphol editing slides for a small 10 minute Jam Session talk.
Was so swamped with work that I forgot to send @charismagic.studio what I wanted to talk about, so she just picked a title and I am now building slides to match 😅
Was so swamped with work that I forgot to send @charismagic.studio what I wanted to talk about, so she just picked a title and I am now building slides to match 😅
"Oscilloscopes & Other Bad Ideas"
I've been so swamped in work that I completely forgot that I am going to give a talk at the @smashingconf.com Jam Session next monday. But with a title like that I already know it's going to be good.
smashingconf.com/freiburg-202...
I've been so swamped in work that I completely forgot that I am going to give a talk at the @smashingconf.com Jam Session next monday. But with a title like that I already know it's going to be good.
smashingconf.com/freiburg-202...
Jam Session — Freiburg in Germany, September 7–10.
The night before the conference kicks off, we’re hosting Jam Session with our dear friends from Reservix, with a few snacks, drinks and micro talks from your fellow attendees! We hope you’ll join us t...
smashingconf.com
September 3, 2026 at 7:52 AM
"Oscilloscopes & Other Bad Ideas"
I've been so swamped in work that I completely forgot that I am going to give a talk at the @smashingconf.com Jam Session next monday. But with a title like that I already know it's going to be good.
smashingconf.com/freiburg-202...
I've been so swamped in work that I completely forgot that I am going to give a talk at the @smashingconf.com Jam Session next monday. But with a title like that I already know it's going to be good.
smashingconf.com/freiburg-202...
Without saying your age, what is your favorite movie that came out when you were 20 years old?
This one was difficult to pick. There were a couple of great ones that year. But this one wins.
This one was difficult to pick. There were a couple of great ones that year. But this one wins.
September 2, 2026 at 9:12 AM
Without saying your age, what is your favorite movie that came out when you were 20 years old?
This one was difficult to pick. There were a couple of great ones that year. But this one wins.
This one was difficult to pick. There were a couple of great ones that year. But this one wins.
I didn’t think I’d ever agree with DHH, but he is totally right. Linux is infiltrated by absolute maniacs.
Anyone still using any of DHH’s products should be taking a very close look at themselves.
Anyone still using any of DHH’s products should be taking a very close look at themselves.
re: omarchy trying to create parallel infra to subvert the linux community and kick trans/female/black people out
i know some people think that sounds crazy but DHH literally is doing a podcast tour saying that is exactly what he's doing lol
i know some people think that sounds crazy but DHH literally is doing a podcast tour saying that is exactly what he's doing lol
September 1, 2026 at 8:10 AM
I didn’t think I’d ever agree with DHH, but he is totally right. Linux is infiltrated by absolute maniacs.
Anyone still using any of DHH’s products should be taking a very close look at themselves.
Anyone still using any of DHH’s products should be taking a very close look at themselves.
Introduce yourself with 10 acts you’ve seen live:
Marillion
Fish
Egdon Heath
Focus
Micheal Jackson
Björk
Massive Attack
Portishead
The Big Push
Ren <- earlier today
And so many more. I could fill the list with just Fish, saw him at least a twenty times.
Marillion
Fish
Egdon Heath
Focus
Micheal Jackson
Björk
Massive Attack
Portishead
The Big Push
Ren <- earlier today
And so many more. I could fill the list with just Fish, saw him at least a twenty times.
Introduce yourself with 10 acts you've seen live:
Less Than Jake
Frank Turner
Bob Dylan
Hans Zimmer
Reel Big Fish
Lemon Jelly
Metallica
Green Day
Public Service Broadcasting
& many swing dance bands
Less Than Jake
Frank Turner
Bob Dylan
Hans Zimmer
Reel Big Fish
Lemon Jelly
Metallica
Green Day
Public Service Broadcasting
& many swing dance bands
August 30, 2026 at 8:36 PM
Introduce yourself with 10 acts you’ve seen live:
Marillion
Fish
Egdon Heath
Focus
Micheal Jackson
Björk
Massive Attack
Portishead
The Big Push
Ren <- earlier today
And so many more. I could fill the list with just Fish, saw him at least a twenty times.
Marillion
Fish
Egdon Heath
Focus
Micheal Jackson
Björk
Massive Attack
Portishead
The Big Push
Ren <- earlier today
And so many more. I could fill the list with just Fish, saw him at least a twenty times.
WebMCP has been an interesting journey for me. Initially not seeing the point, even sceptical it should even be part of the web. Agents can use HTML, just like everybody else, right?
August 29, 2026 at 8:11 PM
WebMCP has been an interesting journey for me. Initially not seeing the point, even sceptical it should even be part of the web. Agents can use HTML, just like everybody else, right?
On my way to London for the weekend - crossing the North Sea - or better the Gulf of The Netherlands, as I’d like to call it. Because apparently you can just change the names of lakes and seas.
August 28, 2026 at 9:33 AM
On my way to London for the weekend - crossing the North Sea - or better the Gulf of The Netherlands, as I’d like to call it. Because apparently you can just change the names of lakes and seas.
CssDOOM on a payment terminal. Yeah… unfortunately not really playable.
August 20, 2026 at 5:16 PM
CssDOOM on a payment terminal. Yeah… unfortunately not really playable.
And @charismagic.studio convinced me to come to @smashingconf.com after all ⭐️⭐️⭐️
I am so looking forward to that, after the conference dry-spell over the summer break. Can't wait - and finally also an opportunity to take the sleeper train back home.
What should I talk about at the Jam Sessions?
I am so looking forward to that, after the conference dry-spell over the summer break. Can't wait - and finally also an opportunity to take the sleeper train back home.
What should I talk about at the Jam Sessions?
August 20, 2026 at 2:52 PM
And @charismagic.studio convinced me to come to @smashingconf.com after all ⭐️⭐️⭐️
I am so looking forward to that, after the conference dry-spell over the summer break. Can't wait - and finally also an opportunity to take the sleeper train back home.
What should I talk about at the Jam Sessions?
I am so looking forward to that, after the conference dry-spell over the summer break. Can't wait - and finally also an opportunity to take the sleeper train back home.
What should I talk about at the Jam Sessions?
Currently busy with performance tweaking of a SQLite based data sync in a native Android app on a payment terminal with low memory and a terrible CPU.
What has my life become?!... I love to write HTML and CSS.
What has my life become?!... I love to write HTML and CSS.
August 20, 2026 at 2:34 PM
Currently busy with performance tweaking of a SQLite based data sync in a native Android app on a payment terminal with low memory and a terrible CPU.
What has my life become?!... I love to write HTML and CSS.
What has my life become?!... I love to write HTML and CSS.
Reposted by Niels Leenheer
@html5test.com making a browser-based cash register work at HalfStack Vienna 2023 🖨️
WebHID. Web Serial. Barcode scanner. Receipt printer.
He’s back in 2026 🎮
🎥 youtu.be/CekjiP5Um90
🎟️ halfstackconf.com/vienna/tickets
WebHID. Web Serial. Barcode scanner. Receipt printer.
He’s back in 2026 🎮
🎥 youtu.be/CekjiP5Um90
🎟️ halfstackconf.com/vienna/tickets
August 19, 2026 at 10:03 PM
@html5test.com making a browser-based cash register work at HalfStack Vienna 2023 🖨️
WebHID. Web Serial. Barcode scanner. Receipt printer.
He’s back in 2026 🎮
🎥 youtu.be/CekjiP5Um90
🎟️ halfstackconf.com/vienna/tickets
WebHID. Web Serial. Barcode scanner. Receipt printer.
He’s back in 2026 🎮
🎥 youtu.be/CekjiP5Um90
🎟️ halfstackconf.com/vienna/tickets
Just when I wanted to take my car this crow swooped down from garage and landed in front of me. Not scared, just looking at me.
After I held my arm up it jumped on my hand and pecked it a couple of times, then looked at me and jumped back on the car.
Weird.
After I held my arm up it jumped on my hand and pecked it a couple of times, then looked at me and jumped back on the car.
Weird.
August 19, 2026 at 3:37 PM
Just when I wanted to take my car this crow swooped down from garage and landed in front of me. Not scared, just looking at me.
After I held my arm up it jumped on my hand and pecked it a couple of times, then looked at me and jumped back on the car.
Weird.
After I held my arm up it jumped on my hand and pecked it a couple of times, then looked at me and jumped back on the car.
Weird.
I visited and spoke at so many great conferences this year, but with the summer break it’s been a while. I get so much energy from conferences and I am starting to miss it.
I’ve been eyeing Smashing Conf in Freiburg. Looks amazing, but already went to Amsterdam, so can’t fully justify going 😢
I’ve been eyeing Smashing Conf in Freiburg. Looks amazing, but already went to Amsterdam, so can’t fully justify going 😢
August 19, 2026 at 2:36 PM
I visited and spoke at so many great conferences this year, but with the summer break it’s been a while. I get so much energy from conferences and I am starting to miss it.
I’ve been eyeing Smashing Conf in Freiburg. Looks amazing, but already went to Amsterdam, so can’t fully justify going 😢
I’ve been eyeing Smashing Conf in Freiburg. Looks amazing, but already went to Amsterdam, so can’t fully justify going 😢
That feeling you get when you are working on the next gen of your product and can finally use modern CSS and get rid of years of legacy code 🤩
Only to discover that that fancy new payment terminal that you want to support runs Chromium 101 and cannot be updated 🤬
Only to discover that that fancy new payment terminal that you want to support runs Chromium 101 and cannot be updated 🤬
August 17, 2026 at 7:57 PM
That feeling you get when you are working on the next gen of your product and can finally use modern CSS and get rid of years of legacy code 🤩
Only to discover that that fancy new payment terminal that you want to support runs Chromium 101 and cannot be updated 🤬
Only to discover that that fancy new payment terminal that you want to support runs Chromium 101 and cannot be updated 🤬
Reposted by Niels Leenheer
Started working on my demo for Fronteers Dark Mode, this is built with CSS scroll-driven animations, no JS 💅 My talk will go into detail on where you can replace JS with CSS!
Tickets are still available: fronteersconf.org
This cool effect is inspired by @thomasaufresne.com → bennettandclive.com
Tickets are still available: fronteersconf.org
This cool effect is inspired by @thomasaufresne.com → bennettandclive.com
August 16, 2026 at 2:55 PM
Started working on my demo for Fronteers Dark Mode, this is built with CSS scroll-driven animations, no JS 💅 My talk will go into detail on where you can replace JS with CSS!
Tickets are still available: fronteersconf.org
This cool effect is inspired by @thomasaufresne.com → bennettandclive.com
Tickets are still available: fronteersconf.org
This cool effect is inspired by @thomasaufresne.com → bennettandclive.com
Reposted by Niels Leenheer
🌙 The Fronteers Dark Mode programme is live!
Join us Oct 2nd in Dordrecht 🇳🇱 for an evening of talks on HTML, CSS, WebAudio, and APIs:
🎤 Barry Pollard
🎤 Anjana Vakil
🎤 Harry Roberts
🎤 Cyd Stumpel
🎤 Heydon Pickering
Hosted by Jake Archibald
🎟️ €99 incl. a 2-course dinner 🥣🥩🐟🥬
👉 fronteersconf.org
Join us Oct 2nd in Dordrecht 🇳🇱 for an evening of talks on HTML, CSS, WebAudio, and APIs:
🎤 Barry Pollard
🎤 Anjana Vakil
🎤 Harry Roberts
🎤 Cyd Stumpel
🎤 Heydon Pickering
Hosted by Jake Archibald
🎟️ €99 incl. a 2-course dinner 🥣🥩🐟🥬
👉 fronteersconf.org
Fronteers Dark Mode, Friday, October 2nd, Dordrecht
Join us at Cinema de Witt in Dordrecht for our after work conference.
fronteersconf.org
July 20, 2026 at 8:49 AM
🌙 The Fronteers Dark Mode programme is live!
Join us Oct 2nd in Dordrecht 🇳🇱 for an evening of talks on HTML, CSS, WebAudio, and APIs:
🎤 Barry Pollard
🎤 Anjana Vakil
🎤 Harry Roberts
🎤 Cyd Stumpel
🎤 Heydon Pickering
Hosted by Jake Archibald
🎟️ €99 incl. a 2-course dinner 🥣🥩🐟🥬
👉 fronteersconf.org
Join us Oct 2nd in Dordrecht 🇳🇱 for an evening of talks on HTML, CSS, WebAudio, and APIs:
🎤 Barry Pollard
🎤 Anjana Vakil
🎤 Harry Roberts
🎤 Cyd Stumpel
🎤 Heydon Pickering
Hosted by Jake Archibald
🎟️ €99 incl. a 2-course dinner 🥣🥩🐟🥬
👉 fronteersconf.org
Just noticed that my Safari bookmarks still have folders for Phonegap, Adobe AIR and Sensha Touch…
Kind of dates me and it shows how often I use bookmarks 😅
Kind of dates me and it shows how often I use bookmarks 😅
July 15, 2026 at 3:03 PM
Just noticed that my Safari bookmarks still have folders for Phonegap, Adobe AIR and Sensha Touch…
Kind of dates me and it shows how often I use bookmarks 😅
Kind of dates me and it shows how often I use bookmarks 😅
Reposted by Niels Leenheer
Do you remember how amazing the #SotB26 speakers were? Best believe that next #SotB27 won’t be any different - amazing speakers and great topics all day!
Go ahead and secure your tickets now so you don’t miss out!
2027.stateofthebrowser.com/tickets/
Go ahead and secure your tickets now so you don’t miss out!
2027.stateofthebrowser.com/tickets/
Tickets | State of the Browser
More information and buying options for tickets.
2027.stateofthebrowser.com
July 7, 2026 at 9:20 AM
Do you remember how amazing the #SotB26 speakers were? Best believe that next #SotB27 won’t be any different - amazing speakers and great topics all day!
Go ahead and secure your tickets now so you don’t miss out!
2027.stateofthebrowser.com/tickets/
Go ahead and secure your tickets now so you don’t miss out!
2027.stateofthebrowser.com/tickets/