Q: how does one test string equality but ignore case?

I've got a situation in which I'd like to compare strings but ignore case. Case is significant for string-equal, and apparently is insensitive to case-fold-search:

(string-equal "string" "StrinG")        ; => nil
(let ((case-fold-search t))
  (string-equal "string" "StrinG"))     ; => nil

I could always preprocess the strings (say, with downcase) before comparing them:

(string-equal (downcase "string")
              (downcase "StrinG"))      ; => t

But that seems like overkill to do two extra function calls every time. Have I overlooked the relevant predicate function somewhere?

  • I used compare-strings and found the following problem. (setq str "title") (cond (compare-strings str "authortitle") do something.) (compare-strings str "title") do something else.) The first compare-strings returns a positive value implying true which is not what I want. Therefore I used the downcase suggestion.
    – user8343
    May 17, 2015 at 15:30

3 Answers 3


You can use compare-strings:

(compare-strings STR1 START1 END1 STR2 START2 END2 &optional IGNORE-CASE)

Use nils for starts and ends to use the whole strings.

  • Thanks; I'd seen that one but didn't realize that one could use nils as you mentioned. I'll leave the question open a little longer in case there's another option that doesn't require 4 extra nils in a function call.
    – Dan
    Mar 30, 2015 at 11:38

Another short alternative:

(cl-equalp "string" "strinG")      ; => t
(cl-equalp "strinG" "this string") ; => nil 
(cl-equalp "word" "buzzword")      ; => nil

equalp from the deprecated cl library is another alternative. From (documentation 'cl-equalp), my emphasis in bold:

like ‘equal’, except that it accepts numerically equal numbers of different types (float vs. integer), and also compares strings case-insensitively.

  • 1
    equalp is not short for cl-equalp - cl-equalp is provided by the cl-lib library, whereas equalp is provided by the deprecated cl library. That the cl library defines it as an alias is an internal implementation detail. I therefore suggest you recommend cl-equalp over equalp. See (info "(cl) Organization").
    – Basil
    Apr 11, 2021 at 20:49
  • Answer updated, as above.
    – dardisco
    Apr 12, 2021 at 22:25

Use string-suffix-p:

(string-suffix-p "string" "strinG" t)

Much simpler and doesn't require 4 nils. It doesn't test if strings are equal per se ((string-suffix-p "word" "buzzword" t) ⇒ t). Although, in some cases this should be sufficient (if you have limited dictionary to check upon).

  • 2
    (string-suffix-p "strinG" "this string" t) also returns t. This is not what the OP wants. I suggest you either modify or delete this answer.
    – Tobias
    Jan 28, 2016 at 22:09
  • Answer updated. I will leave it because string-{prefix,suffix}-p can useful in many ways: test if word at point is given keyboard (in SQL for example where case can be mixed) etc.
    – rgtk
    Jan 29, 2016 at 15:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.