Trigger.new vs Trigger.newMap — Key Differences in Salesforce Apex Triggers

Posted by Vinay Vernekar 23rd October 2025

Overview

When writing Apex triggers in Salesforce you’ll often work with context variables that provide the records being processed. Two of the most commonly used context variables are Trigger.new and Trigger.newMap. Understanding the differences between them helps you write clearer, safer, and more efficient trigger code.

What is Trigger.new?

Trigger.new is a List containing the new versions of the records currently being processed by the trigger. Use it when you need to iterate over the records in order or perform operations that rely on list semantics.

// Example: Iterate and validate fields
for (Account acc : Trigger.new) {
if (acc.AnnualRevenue < 0) {
acc.addError('Annual Revenue cannot be negative');
}
}

What is Trigger.newMap?

Trigger.newMap is a Map that maps record Ids to their new sObject values. It’s useful when you need to quickly look up a record by Id (O(1) lookups) — for example, when comparing old vs new values across related collections or avoiding nested loops.

// Example: Fast lookup by Id
Account changedAcc = Trigger.newMap.get(someAccountId);
if (changedAcc != null) {
// Work with the changedAcc
}

Availability & Context Differences

Knowing which context variables are available in each trigger event is important:

  • Trigger.new is available in before insert, after insert, before update, after update, and after undelete. It is NOT available in delete triggers.
  • Trigger.newMap is available in before update, after update, after undelete, and after insert (where Ids are assigned). It is NOT available in before insert if the records don’t yet have Ids, and it is NOT available in delete triggers (use Trigger.old / Trigger.oldMap instead).

When to use each

Choose based on your need:

  • Use Trigger.new when you need to preserve order, transform the entire list, or when working in contexts where Ids are not yet assigned (e.g., before insert validation).
  • Use Trigger.newMap when you need fast lookup by Id, when comparing to Trigger.oldMap during updates, or when you want to avoid nested loops to improve performance.

Practical example: update-based comparison

Compare field changes during an update using Trigger.oldMap and Trigger.newMap:

// Trigger on Account (after update)
for (Id accId : Trigger.newMap.keySet()) {
Account newAcc = (Account)Trigger.newMap.get(accId);
Account oldAcc = (Account)Trigger.oldMap.get(accId);
if (newAcc.AnnualRevenue != oldAcc.AnnualRevenue) {
// Revenue changed — take action
}
}

Performance considerations

Maps allow direct lookups which avoids expensive nested loops. When comparing or aggregating across related collections, prefer maps to keep CPU time and heap usage lower.

Quick reference

  • Trigger.new: List<sObject>, ordered, used for iteration and operations when Ids may not exist.
  • Trigger.newMap: Map<Id, sObject>, fast lookups by Id, best for comparisons and cross-referencing.

Understanding both will make your Apex triggers simpler, more maintainable, and performant.

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