CodeRunner 4 4+

Fantastic lightweight editor+runner

Developers will always scoff at apps like these (especially ones whose primary notability derives from the Mac App Store—normally a bit sketchy), which make you pay for what you could likely get for free from such popular editors as Sublime, Atom, Notepad++, Vim, etc. But I can whole-heartedly vouch for the legitimacy of Coderunner on all fronts. It is virtually bug-free, has a dead-simple interface, is extremely fast, is delightfully customizable, has excellent syntax highlighting for a good variety of languages, and most importantly, lets you run your programs with the touch of a button, no strings attached.

I personally use it for small programs and self-contained bits of code—it serves as an excellent, speedy testing groundy to dump snippets into or to build up sections of a larger project. It is also a fine editor for HTML and Markdown, as it renders it in the output window when you press run. Of course, I’ll tend toward full IDE’s for larger, more interconnected projects, but when it comes to single-file programs, I find it faster and more pleasant than the more popular editors.

May cause problems with Adobe Creative Cloud

But that may be because I downloaded the off AppStore debug version (it is free). After using that creative cloud had a problem and I do use my adobe apps quite a bit.
I bought the app because I did not want to download big sur to download XCode. They are both huge downloads and would use up my satelittle internet limits.
I had no problems running C and swift programs.
It is a bit easier to use to make corrections in php than in Dreamwearver. Though you can't see the live pages in coderunner it is easier to manuver to the lines you need to change.

Can’t even correctly parse simple HTML

I tried this on a pretty simple HTML page that was working fine. This app complained about some “stray closing tag”s on some </div> tags that were, in fact, correctly matched, and the app provides no way to get any more info on why it thinks they’re stray.
There is no way to select an open tag and ask the app to show what it thinks is the closing tag, so the error isn’t even useful if it’s right.
The UI is awful. The “back” button, which every single app in the world puts on the left side, this app puts on the far right side.
There is a search function that searches all files, but there is no way to select text and put it into that search box! You have to copy the text, click in the search box, hit delete to empty it, then paste in the text, and then, finally, click the search button. Ridiculous.
$20 for an app that has about $1.98 worth of features.

Developer Response ,

Hi. You can double-click the angle bracket of the opening HTML tag, and the app will select to the closing tag. You can also click on the tag name when selected and it will highlight the closing tag. Additionally, you can use the "Select to Delimiters" menu item when inside of a tag pair. If these don't work and you're seeing error messages, it is almost certain that your HTML file contains mistakes, even though modern web browsers are able to render it correctly. If you'd rather just get rid of the stray tag error message, you can right-click the error and choose "Ignore ... in Document/Globally".

If you want to move the back/forward navigation buttons in the toolbar to the left side, you can do so by right-clicking the toolbar and choosing "Customize Toolbar..." (like in most macOS apps.)

For search across files and folders, there's lots of operations with keyboard shortcuts under the "Find" menu, likely the one you're looking for is "Search for Selected Text in File System" (Command-Shift-F).