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Jens Oliver Meiert
Jens Oliver Meiert

Posted on • Originally published at

The 3-Second Frontend Developer Test

If you had to hire a frontend developer and had just one question, what would you ask?

I recommend the 3-second frontend developer test:

Do you validate [your HTML and CSS code]?

A truthful answer gives you more than any other question would do.

Why is that?

The answer tells you several important things:

  1. Foundational knowledge: Through validating and the correcting of validation issues, the developer is sure to have and to maintain foundational knowledge of development with HTML and CSS. A developer not validating may or may not have this knowledge.

  2. Base quality: Assuming a validation routine, validation ensures base quality of the output. A developer who doesn’t validate, on the other hand, is guaranteed to deliver inferior quality. Guaranteed, because even with perfect HTML and CSS knowledge, they will make mistakes. No one writes perfect code, all the time, and a senior frontend developer is not permitted an excuse from checking their code on issues.

  3. Professional conduct: Frontend development is open to everyone. To this day, there is nothing tangible that differentiates a professional frontend developer from a wannabe or amateur developer. (I’m close to recording how my houseplants write HTML and CSS less invalid than that of the most popular sites.) Nothing differentiates professional and amateur developers—except for a habit of validation. A developer who doesn’t validate and who doesn’t ship valid code is not a professional developer.

  4. Aspiration: The practice of validation suggests aspiration; the developer is not content with using HTML and CSS incorrectly, with not using them professionally. A developer not validating their HTML and CSS does not demonstrate any more aspiration than a driver revving their car’s engine in the central business district. That may appear competitive, but they’re a far cry from a professional race driver.

Validation is important. Validation is the thing that makes frontend developers professional frontend developers. Validation is therefore a key criterion for hiring. By applying it, you set a well-defined bar, and you help the field of frontend development level up as a profession and a craft. Be a frontend developer who validates and ships valid HTML and CSS; hire frontend developers who validate and ship valid HTML and CSS.

The few exceptions do prove the rule. They may consist in pending updates to validators, but can also relate to false positives. They do not consist in a developer or an organization putting themselves above the rule—especially not when their code is shared. As the impact is larger, even higher standards apply here. The time of unconditionally accepted sloppiness in professional frontend development must end.

If you like another perspective at the benefits of validation, Why Validate Your Pages? tries to be super-comprehensive. If you like a list of (web-based) validators,’s “conformance” section features the main ones, covering other languages as well (disclosure: I run

Top comments (3)

grahamthedev profile image
GrahamTheDev • Edited

First thing I did was validate (not so great on the HTML front) then I found your personal page and all was good again 😋

My old site - passes both (which is quite surprising as I broke that site over a year ago and lost most of the content)!

We should start a club as I am sure sites that are valid are few and far between! 🤣

As for the article...I actually think this idea is genius! Valid HTML normally means a site is at least somewhat accessible and normally means it is somewhat SEO optimised too so it is a very quick "birds eye view" of a developer. Stealing this! ❤

The "15 second test" could include (or and that way we can really separate the pack (I might be biased as I know will still do great in any of those tests 😋)!

j9t profile image
Jens Oliver Meiert

Thanks for the feedback! I can’t officially comment for Jimdo as I’ve been leaving them, but having been the engineering manager for I will say that valid output has been a priority for us, too.

(Interestingly, what—and other sites, too—may sometimes deal with is third-party code that “invalidates” the output. One may be surprised how hard it can be to get such problems fixed, even if one submits a patch.)

Valid output is not a guarantee for anything other than syntax correctness and a degree of conformance—a minimum expectation for a professional—, but you’re right, it does guard against other problems, too, including some around accessibility and search engine friendliness.

I love you suggesting other tests, then. It’s exactly the types of ideas and conversations we should be having 🙏

grahamthedev profile image

Ah so are you moving on to another company or branching out on your own?

Great point about third party actually raises a really interesting question about the vetting process when choosing third party code! Do you add allowances or do you discount third party code that doesn’t align with your in house validation criteria.

Who would have thought a simple 3 second test would give me so much food for thought! ❤️