Should you capitalise job titles? The rule that settles it
It looks like a tiny detail until you're staring at your own resume at 11pm wondering whether "marketing manager" needs capitals. Recruiters do notice inconsistency, mostly because it's the easiest kind of sloppiness to spot. Here is the rule, and it fits in one sentence.
Capitalise a job title when it sits directly before or in place of a person's name, or when it appears as a heading. Leave it lowercase when you're describing the role in a normal sentence.
The rule in practice
On your resume, titles are headings. "Senior Data Engineer, Canva" is a label, not a sentence, so it takes capitals. Same for the headline under your name and the position field in an application form.
In your cover letter, you're writing prose. "I spent four years as a senior data engineer building streaming pipelines" reads naturally in lowercase. "I'm applying for the Senior Data Engineer position" keeps the capitals because you're naming the specific advertised role, effectively quoting the ad.
Job ads themselves are inconsistent, which is where most of the confusion comes from. Don't inherit their style. Pick the rule above and apply it everywhere, because consistency is what a reader actually registers.
The edge cases people ask about
Seniority words follow the title they're attached to: "Senior Product Manager" as a heading, "a senior product manager" in a sentence. Acronyms stay capitalised everywhere: CEO, CTO, APS6. Fields and departments are lowercase unless they contain a proper noun, so "data engineering" but "the Python team".
One more worth knowing for Australian applicants: public service classifications like APS6 or EL1 are part of the official title and always keep their form, wherever they appear.
Why we bothered writing this down
When Applyable typesets a resume, titles are treated as headings and capitalised consistently, and the cover letter generator writes titles in sentence case unless it's naming the advertised role. You get the rule above by default. But it's your name on the document, so it seemed fair to explain what the rule is and why.