Explain the difference between ISNULL() and ISBLANK()? | CRM Curator

ISNULL() and ISBLANK() look interchangeable until you point them at a text field. They handle empty strings differently, and that single difference is why Salesforce documentation tells you to use ISBLANK() for new formulas.

The one-line answer

ISNULL(field) returns TRUE only when the field is null. It returns FALSE for an empty text string ("").
ISBLANK(field) returns TRUE when the field is null or contains an empty string with no characters.

Why empty string vs null matters in Salesforce

Salesforce treats text fields specially. A blank Text or Text Area in the UI is stored as an empty string, not as null. So:

ISNULL(Description__c)   // returns FALSE — the field holds ""
ISBLANK(Description__c)  // returns TRUE  — handles "" as blank

For number, currency, date, datetime, percent, and checkbox fields, the two functions are functionally equivalent because those types can’t hold an empty string — they’re either null or have a value.

When to use which

Use `ISBLANK()` for	Use `ISNULL()` for
Anything in new formulas — it’s the recommended function	Backwards compatibility with very old formulas you don’t want to touch
Text fields, Text Area, Email, URL, Phone	Never preferred, except in legacy code
Mixed-type comparisons where you might add a Text field later	—

Quick reference table

Field type	Value	`ISNULL()`	`ISBLANK()`
Text	`null`	TRUE	TRUE
Text	`""` (empty)	FALSE	TRUE
Text	`"hello"`	FALSE	FALSE
Number	`null`	TRUE	TRUE
Number	`0`	FALSE	FALSE
Checkbox	`false`	FALSE	FALSE — checkboxes are never blank

The interview trap

Candidates who say “they’re the same” fail this one. The interviewer will follow up: “What about a text field that’s been cleared?” The right answer is to call out the empty-string case and recommend ISBLANK() by default.

Bonus: `BLANKVALUE` vs `NULLVALUE`

The same logic applies to the value-substitution variants:

BLANKVALUE(field, default) returns default when the field is null or an empty text string
NULLVALUE(field, default) only kicks in when the field is null

Use BLANKVALUE for text, NULLVALUE is rarely the right call in modern formulas.

Verified against: Salesforce Help — ISBLANK vs ISNULL. Last reviewed 2026-05-17 for Spring ‘26 release.