Can I withdraw after accepting a job offer but before signing the contract?

Be careful: in Germany an employment contract does not need a signed document to exist. If the employer offered you the job with the essential terms (position, start date, salary) and you clearly accepted – by e-mail, on the phone or in person – a contract may already have been concluded. The written document that follows is then only the documentation required by the Nachweisgesetz, not the contract itself.

What that means:

• If no contract has been concluded yet (for example, you only said you were interested or terms were still open), you can simply inform the employer that you will not take the job.
• If a contract exists, you cannot just "withdraw"; you would have to terminate it. Before the start date this is usually possible with the notice period agreed for the probation period (two weeks during an agreed probation period, § 622 (3) BGB), unless the contract excludes termination before the start date. Some contracts contain a contractual penalty for not starting, which can be enforced if it is validly agreed.
• In practice most employers accept a prompt, polite written cancellation and do not pursue claims, but they are not obliged to.

Recommendation: decide quickly, tell the employer in writing as soon as possible, and keep the message short and professional. If you have already received a signed contract, read its termination clause before you reply.