Boolean Search String Builder
List the concepts in your research question and the synonyms for each, and get a correctly bracketed Boolean search — synonyms joined with OR, concepts with AND, exclusions with NOT — written out in the syntax of Google Scholar, PubMed, EBSCOhost, ProQuest, Web of Science and Scopus, each with its own copy button and notes on what the database cannot do. Everything runs in your browser. Free, no sign-up.
Concepts
One concept per row. Synonyms inside a row are joined with OR; the rows are joined with AND. Multi-word terms are quoted for you. Add * to truncate — nurs* finds nurse, nurses and nursing. For proximity, put ~ and a number between two words: sleep ~3 deprivation.
Your search strings
Type at least one term into a concept to build the search strings.
How to Use the Boolean Search String Builder
- 1. Split your question into concepts. "Sleep problems in university students" is two: sleep problems, and students. Give each concept its own row.
- 2. List synonyms, one per line. Spelling variants, plurals, acronyms, related terms. Multi-word terms are quoted for you; add an asterisk to truncate (student* finds students); put ~ and a number between two words for proximity (sleep ~3 deprivation).
- 3. Choose where each concept is searched. Default fields, title only, title or abstract, or subject headings such as MeSH. Add anything to exclude in the NOT box.
- 4. Copy the version for your database. Each card shows the string, its length, and notes where the database handles something differently. Paste it into the database's advanced search.
How Boolean Logic Builds a Search
OR widens: it finds records with any of its terms, so it joins the synonyms for one concept. AND narrows: each record must contain every concept. NOT removes records that contain a term. Parentheses decide what goes with what, and they matter more than they look: databases read mixed operators in different orders — ProQuest and Web of Science apply AND before OR, and Scopus, which long applied OR first, announced a switch to AND first for 2025–26 — so the builder brackets every OR group to make the string mean the same thing everywhere, whatever the order of the day.
Quotation marks keep a phrase together. Truncation with * catches word endings: nurs* finds nurse, nurses and nursing. Proximity operators find two words close to each other in any order — narrower than AND, looser than a phrase.
One Search, Six Syntaxes
| Interface | Title or abstract | Truncation | Proximity | Exclude |
|---|---|---|---|---|
| Google Scholar | intitle: for titles; no abstract field | None — automatic stemming | None | -term |
| PubMed | term[tiab] | * after at least 4 letters | "a b"[tiab:~3] | NOT |
| EBSCOhost | TI (…) OR AB (…); XB in some databases | * | a N3 b | NOT |
| ProQuest | TI,AB(…) | * (up to 5 characters), [*n] | a NEAR/3 b | NOT |
| Web of Science | TI=(…) OR AB=(…); TS= for topic | * | a NEAR/3 b | NOT |
| Scopus | TITLE-ABS(…); TITLE-ABS-KEY(…) | * | a W/3 b | AND NOT, at the end |
Google Scholar also cuts queries off at about 256 characters, and PubMed proximity searches accept no wildcards.
Example: Sleep Problems in University Students
Click Load an example and the builder fills two concepts — sleep quality, insomnia and sleep ~3 deprivation, searched in title or abstract; and student*, undergraduate* and college students in the default fields — with child* excluded. Three of the six strings it produces:
The same search, three ways
PubMed
("sleep quality"[tiab] OR insomnia[tiab] OR "sleep deprivation"[tiab:~3]) AND (student* OR undergraduate* OR "college students") NOT child*
Scopus
TITLE-ABS("sleep quality" OR insomnia OR (sleep W/3 deprivation)) AND TITLE-ABS-KEY(student* OR undergraduate* OR "college students") AND NOT TITLE-ABS-KEY(child*)
Google Scholar
("sleep quality" OR insomnia OR "sleep deprivation") (student OR undergraduate OR "college students") -child
The Google Scholar version shows the compromises: no truncation, so the asterisks are gone; no proximity, so the pair became a phrase; and no abstract field, so the first concept searches everywhere.
Common Mistakes
- Leaving out the parentheses. sleep OR insomnia AND student means different things in different databases. Bracket every OR group.
- Truncating too early. cat* finds catheter and category. In PubMed, fewer than four letters before the asterisk switches truncation off entirely.
- Quoting single words in PubMed. Quotation marks bypass Automatic Term Mapping, so "cancer" misses the MeSH heading the unquoted word would add.
- Excluding too much with NOT. NOT child* also drops studies of adults that mention children once. Exclude only when you have checked what you lose.
- Pasting one database's syntax into another. TS= means nothing to Scopus and [tiab] means nothing to EBSCO. Copy the card for the database you are in.
Frequently Asked Questions
- What is a Boolean search string?
- It is a search written with the operators AND, OR and NOT, plus parentheses, phrases and truncation, so a database retrieves exactly the combination of concepts you want. A typical string has one bracketed OR group of synonyms per concept, joined with AND: ("sleep quality" OR insomnia) AND (student* OR undergraduate*).
- How do I write a search string for a literature review?
- Break the question into two or three concepts, often from a PICO question. For each, gather synonyms from key papers and the database's thesaurus, join them with OR, and join the concepts with AND. Test the string, check that known relevant papers turn up, and record the final version for each database so the search can be reported and repeated.
- Does Google Scholar support Boolean operators?
- Partly. It understands OR in capitals, treats a space as AND, excludes with a minus sign, and keeps quoted phrases together, but it has no truncation, no proximity operators, no reliable nesting of parentheses, and it cuts queries off at about 256 characters. Use it alongside a bibliographic database, not instead of one.
- What does N5 mean in an EBSCO search?
- N5 is EBSCOhost's near operator: the two words must appear within five words of each other, in either order, so tax N5 reform finds "tax reform" and "reform of income tax". W5 does the same but keeps the words in the order typed. ProQuest and Web of Science write NEAR/5, Scopus writes W/5, and PubMed writes the pair in quotes with [tiab:~5].
- What is the difference between TS= in Web of Science and TITLE-ABS-KEY in Scopus?
- Both search a record's title, abstract and keywords. Web of Science's Topic field (TS=) covers title, abstract, author keywords and Keywords Plus; Scopus's TITLE-ABS-KEY covers title, abstract, author keywords and Scopus's indexed keywords. Neither searches the full text, which is why they are the usual starting fields for a systematic search.
- Should I use subject headings or keywords?
- Both, joined with OR inside the same concept. Subject headings such as MeSH find papers indexed under a concept whatever words the authors used; keywords find recent papers not yet indexed and terms the thesaurus lacks. Set a row to subject headings for the controlled terms and keep a second row of keywords, or list both in one row for databases that take mixed searches.