You should (almost) always have several resumes, ideally a completely customized one for each job you apply for.

When you share your resume with an employer, the first thing they are going to do is read it and see how closely it matches the job description. They are trying to see similar words in both documents, and make sure that the skills and experiences on the resumé match the requirements listed in the job description. Because each job description is unique, and might use different language even from a similar role at a different company, the language you use in your resume will also be unique.

For example, one role might ask you to talk about your “customer service” while a similar role at another company might ask for “helping patrons.” When you talk about your experience, you need to make sure you mirror that language. Don’t say “helping patrons” if they ask for “customer service” because most resume parsers won’t know the difference, and some humans may miss it if they’re not reading carefully.

You also need to remove information from each resume that doesn’t relate directly to the job. You probably have a variety of skills, but you should only include the relevant information for the job you are applying for. Any skills and experiences you have that wouldn’t contribute to your ability to do that job, should be removed from that resumé.

The possible exception to this rule is volunteer experience, which may be used to show your interests or demonstrate your commitment to service. Ideally, that experience would relate to their field your applying for, but it might not always line up directly.

The only time you might not have several customized resumes is if you’re applying to a role where there is a single certification that determines eligibility for the role. Medical positions like dental or nursing assistants and tradecrafts like welding or plumbing might be more concerned with what certifications you hold and where you worked in the past, but might not have highly specific job descriptions for you to react to. It’s still recommended that you read the job description carefully, and see if you need to add or tweak any bullets to make them match as closely as possible to the job description.