Bad Practice

Bad practice is a set of techniques, especially common ones, that result in otherwise avoidable adverse effects.

Using INDEX+MATCH instead of modern alternatives

While INDEX+MATCH is a common pattern in Excel, it is often a bad practice in Google Sheets because INDEX does not support array arguments for its row or column indices. This prevents the formula from “broadcasting” results when used inside an ARRAYFORMULA. Use XLOOKUP or VLOOKUP instead, as they are more concise and natively support array outputs.

Using LEN for blank cell detection

Using LEN(A1) to check if a cell is empty is less efficient and less semantically clear than ISBLANK(A1). Additionally, LEN returns 0 for cells containing empty strings "", which are not truly blank/null values.

Runaway ARRAYFORMULA without controls

Using ARRAYFORMULA without output control can generate 50,000 rows of results, severely degrading sheet performance. Always use control structures:

• IF(ISBLANK(...)) to limit expansion
• ARRAY_CONSTRAIN to cap output size

Storing numbers or dates as text

Storing numeric data as text prevents mathematical operations, proper sorting, and date/time arithmetic. Convert text to proper types using VALUE(), DATEVALUE(), or TIMEVALUE().

See Also

• Good practice — recommended techniques
• Array-enabled functions — proper ARRAYFORMULA usage
• Type coercion — how types are converted