How can I reconstruct and document a search strategy I ran informally so it becomes reproducible?

You can reconstruct an informal search by rebuilding it as a written record of sources, dates, exact strings, field tags, filters, and result counts, then rerunning it to confirm it produces comparable results. The Cochrane Handbook treats documenting searches as part of the search process for systematic reviews, and PRISMA 2020 provides a checklist and flow diagrams for transparent reporting of methods and what studies were found and included. Use those two frameworks to decide what your methods paragraph and appendix must contain.

Rebuild the record

1. List every source you actually searched. Name each database and any other source, such as reference lists, that you used. The Cochrane Handbook covers selecting sources and searching reference lists and other sources, so record those alongside databases.
2. Record the date of each search. A rerun only means something if the reader knows when the original results were captured.
3. Write the exact string for each source. Copy the query as it was entered, including phrase searching and field tags. The PubMed User Guide documents field tags, phrase searching, filters, and Advanced Search, so capture which of these your string used.
4. Record filters and limits separately from the string. Filters change the result set without changing the query text, so list them as their own field.
5. Record the result count for each source. This is the number your rerun must be compared against.

Rerun and compare

Rerun each recorded string with the same field tags and filters, then compare the new result count with the recorded count. A comparable count supports the record; a different count leaves the strategy unresolved, so note the difference and check whether the string, tags, or filters were transcribed correctly before deciding what changed. PubMed's saved searches and Advanced Search can help you store and re-execute a strategy you have now written down.

Write the methods paragraph and appendix

The methods paragraph should state the sources searched, the search dates, and how records were managed. The appendix should carry the full strings, field tags, filters, and result counts per source so a reviewer can repeat each search. PRISMA 2020's checklist and flow diagram give you the reporting structure for what was found and included; use the flow diagram to show how records moved from search results to included studies.