A developer's insurance problem is that the damage is invisible. Nothing burns and nobody falls; a system does the wrong thing and somebody loses money, which is a category of loss only one kind of policy is built for.
Professional indemnity does the work
A defect that takes a client's service down, a project delivered late, a migration that loses records, a feature that does not do what the specification said: each is an economic loss arising from the service. Professional indemnity answers for it, written on a claims made basis, which means the policy in force when the claim arrives responds rather than the one in force when the code shipped. A developer between contracts should keep cover running for that reason alone.
Where cyber picks up
If the developer holds client data, has credentials into client systems or hosts anything, the exposure crosses into cyber: a breach, a ransomware event, notification costs, forensic investigation and the business interruption of your own systems being down. Technology policies increasingly combine the two because the argument over which responds to a breach caused by a coding error helps nobody, and a combined wording removes the seam.
Contract clauses that set the numbers
Client contracts for software work typically name a professional indemnity limit and often a cyber limit, cap the developer's liability at a multiple of fees, and require cover to be maintained for a period after the work ends. That last requirement is a run off obligation with a real cost, and it is regularly agreed without anybody pricing it. Reading the liability cap alongside the insurance clause is worth doing, because the two are sometimes inconsistent in the client's own favour.
Open source, licences and intellectual property
Claims that delivered code infringed a third party's rights, or that an open source licence obligation was missed and forced disclosure, are real and are handled inconsistently across wordings. Some policies cover unintentional infringement, some exclude intellectual property outright. A developer who signs contracts containing an intellectual property indemnity should establish which kind of policy they hold before signing the next one.
Questions people ask about software developer insurance
Does a software developer need public liability?
Rarely for the real risk, though client contracts often require it and it applies when working at a client's site.
Is a bug that takes a client offline covered?
Under professional indemnity, where the client's loss flows from the service. Your own downtime is a cyber or business interruption question.
What is run off cover and why do contracts ask for it?
Cover maintained after the work ends, because claims made policies respond when the claim arrives. Contracts often require it for several years and it has a cost worth pricing.