What is a custom GPT?
A custom GPT is a version of ChatGPT that someone has configured for a specific job with saved instructions, reference files and optional connections, so staff can reuse the same setup instead of writing prompts from scratch each time.
OpenAI lets ChatGPT users build these without code: you describe the role, upload reference documents and set conversation starters. Other platforms offer similar features under different names, such as Claude Projects and Gemini Gems. The idea is the same across them: package a tested prompt and its source material so the whole team gets consistent results.
Custom GPTs are a good low-cost way to standardize repetitive writing and reference tasks, like drafting job postings in your house style or answering questions about the employee handbook. They are a poor fit for anything that needs live data from your systems, strict rules, or an audit trail of who did what, since they live inside a chat tool.
Check the data terms of your plan before uploading client files. Business and enterprise tiers generally handle data differently from personal accounts, and those differences matter for HIPAA, attorney-client privilege and the FTC Safeguards Rule. Decide who owns each custom GPT, how its files are kept current, and what happens to it when that person leaves.
Example
For example, a Denver roofing contractor could build a custom GPT loaded with its warranty terms, material spec sheets and approved tone examples. Office staff use it to draft replies to homeowner questions after hail storms. Every draft is read by the office manager before sending, and anything about insurance claims goes to the owner.