Yes, by hand. Custom instructions are plain text, so nothing stops you writing one good block and pasting it into ChatGPT, a Claude project, and Gemini’s saved info. The real questions are whether the block is any good, and who keeps it current.
Most custom instructions are wish lists. "Be concise. No fluff." The blocks that actually change how an AI treats you say how you work: whether you want the whole plan up front or step by step, what you are building, what steadies you when something breaks. Write that once and every assistant gets noticeably better on the first message.
Paste the same block into four apps and you now own four unsynchronized copies. Your projects change, your patterns change, and each copy rots at its own speed. Six months in, every AI holds a slightly different stale version of you, and none of them knows which is true.
A Pupul profile is that block, done properly: held in one place, dated entry by entry so nobody has to take your word for when a line was written, and pasted or granted into any AI. Update it once and the verify link always covers the current version. Revoke it once and every copy dies together. It is free to start.
Every platform named on this page will hand you your own export if you ask. The free Count opens that file in this browser and prints what is in it: how many records, over how long, and which categories you were filed under. It counts, and it shows you the shape of the file. No account, no email field, and the file never leaves your device.
Open the free CountThe Reading, the paid page that reads a file back to you in plain sentences with a receipt on every line, is the step after. 6.99 a week or 69.99 a year, and the Count stays free either way.
ChatGPT: Settings, Personalization, Custom Instructions. Claude: project instructions or your first message. Gemini: saved info. All accept plain pasted text, which is what makes a portable block possible.
Credentials, financial details, and anything about how you fold under pressure. That last layer is exactly what a manipulative product would want, which is why a Pupul profile has no field for it on any outbound surface.