# Cannot Create Classes

**URL:** https://discourse.processing.org/t/cannot-create-classes/8756
**Category:** Beginners
**Created:** [February 27, 2019, 9:24am UTC](https://discourse.processing.org/t/cannot-create-classes/8756 "2019-02-27T09:24:31Z")
**Posts on this page:** 1
**Showing post:** 17

<div class="post-metadata">

### Author: ![GoToLoop](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/gotoloop/32/86_2.png) [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [March 1, 2019, 11:41am UTC](https://discourse.processing.org/t/cannot-create-classes/8756/17 "2019-03-01T11:41:38Z")

</div>

> [@Californ1a](#):
>
> You can also use the method @GoToLoop posted, but that doesn’t use a webserver and may also cause some issues depending on what your code is doing (which is mentioned in the video).

AFAIK, Firefox-based browsers treat the `file://` URL scheme the same way as the `http://` URL scheme. 🦊

Thus far I haven’t found any issues at all when running Processing sketches on Firefox under its `file://` URL scheme. 🥳

Firefox-based browsers use the Gecko Spidermonkey JS engine. 🕷

But if we prefer/need to test JS on the Chrome’s Blink V8 engine instead, we can use the Vivaldi browser: 🎼

> **[Vivaldi Browser | Powerful, Personal and Private web browser](https://vivaldi.com)**
>
> It’s a web browser. But fun. It comes with a bunch of clever features built-in. It’s super flexible and does not track you. Get the Vivaldi browser for desktop, mobile, and your car!

Similarly to Firefox, Vivaldi doesn’t restrict the `file://` URL scheme either. 👌

However, anything that relies on the Fetch API fails on the V8 JS engine, b/c they’ve deliberately disallowed the `file://` URL scheme on this particular API: 🤬

[Bugs.Chromium.org/p/chromium/issues/detail?id=810400](http://Bugs.Chromium.org/p/chromium/issues/detail?id=810400)

---

_[View the full topic](https://discourse.processing.org/t/cannot-create-classes/8756)._