The $rtrim operator removes trailing characters from a string in MongoDB aggregation expressions. By default it strips whitespace from the right; optionally you can specify which characters to remove.
End of string only.
input + optional chars.
Default trim behavior.
Strip suffixes like /.
URLs, imports, codes.
Right vs left end.
In MongoDB’s aggregation framework, the $rtrim operator trims characters from the right side of a string. For example, "MongoDB " becomes "MongoDB" when you trim trailing whitespace. This is useful when cleaning imported data, normalizing URLs, or removing trailing punctuation from codes.
Think of $rtrim as MongoDB’s pipeline version of trimming only the end of a string — similar in spirit to JavaScript’s String.prototype.trimEnd(), with an optional custom character set.
$rtrim only affects the right end. Leading spaces stay in place. Use $trim to clean both sides, or $ltrim for the left end only.
The $rtrim operator takes an object with input and an optional chars field:
{
$rtrim: {
input: <expression>,
chars: <optional string>
}
}// Trim trailing whitespace (default)
{ $rtrim: { input: "$name" } }
// Trim specific trailing characters
{ $rtrim: {
input: "$url",
chars: "/"
}}
// Trim a literal string
{ $rtrim: { input: "hello " } }input — required; the string expression to trim (field reference or literal).chars — optional; characters to remove from the right. If omitted, whitespace is trimmed.input is null, the result is null.$project, $addFields, or $set." hello " + $ltrim → "hello "" hello " + $rtrim → " hello"" hello " + $trim → "hello"$rtrim| Question | Answer |
|---|---|
| Operator type | Aggregation expression operator (string) |
| Syntax | { $rtrim: { input: ..., chars: ... } } |
| Default behavior | Remove trailing Unicode whitespace |
| Custom trim | Pass chars with characters to strip |
| Common stages | $project, $addFields, $set |
{
$rtrim: {
input: "$name"
}
}Default right trim
{
$rtrim: {
input: "$url",
chars: "/"
}
}Strip trailing /
{
$rtrim: {
input: "hi "
}
}Returns "hi"
{
$rtrim: {
input: null
}
}Returns null
Walk through a sites collection with messy string fields and clean trailing characters with $rtrim.
Remove trailing whitespace from imported site names using $project.
Suppose you have a sites collection with untrimmed name and url fields:
[
{
"_id": 1,
"name": "CodeToFun ",
"url": "https://codetofun.com///"
},
{
"_id": 2,
"name": "MongoDB Docs\t",
"url": "https://mongodb.com/docs/"
},
{
"_id": 3,
"name": "Example Site ",
"url": "https://example.com"
}
]Trim spaces and tabs from the end of each site name:
db.sites.aggregate([
{
$project: {
name: 1,
cleanName: {
$rtrim: { input: "$name" }
}
}
}
])chars, MongoDB removes trailing whitespace (spaces, tabs, etc.).Strip trailing slashes from URL paths for consistent linking.
Remove trailing / characters from URL values:
db.sites.aggregate([
{
$project: {
url: 1,
cleanUrl: {
$rtrim: {
input: "$url",
chars: "/"
}
}
}
}
])The chars argument defines which characters to strip from the right. MongoDB removes them one by one from the end until it hits a character not in the set.
Apply $rtrim to multiple fields in a single $addFields stage:
db.sites.aggregate([
{
$addFields: {
name: {
$rtrim: { input: "$name" }
},
url: {
$rtrim: {
input: "$url",
chars: "/"
}
}
}
}
])$addFields overwrites the existing fields with cleaned values. Use this when you want to normalize data in place before downstream stages or export.
Trim a fixed string inside an expression:
db.sites.aggregate([
{
$project: {
demo: {
$rtrim: { input: "MongoDB " }
}
}
}
])The input can be a literal string, not just a field path. Useful inside nested expressions and for testing trim logic.
See how each trim operator affects the same string:
db.sites.aggregate([
{
$project: {
original: " MongoDB ",
leftOnly: {
$ltrim: { input: " MongoDB " }
},
rightOnly: {
$rtrim: { input: " MongoDB " }
}
}
}
])
// leftOnly: "MongoDB "
// rightOnly: " MongoDB"$rtrim is precise when you only need to fix the end of a string. For both sides, use $trim when that page is available in the series.
$project for reports and APIs."active " matches "active" on the right side.$rtrim WorksThe input expression resolves to a string from a field or literal.
Uses chars if provided; otherwise defaults to Unicode whitespace.
Strips matching characters from the end until the first non-matching character from the right.
The expression returns the string with trailing characters removed.
The $rtrim operator is a practical string-cleaning tool for MongoDB aggregation pipelines. Use it to remove trailing whitespace or custom suffix characters from field values before display, matching, or further string operations.
Remember: input is required, chars is optional, and only the right side is affected. For full whitespace cleanup on both ends, use $trim. Next in the series: $sampleRate.
$rtrim when only trailing characters need removalchars for standard whitespace cleanupchars: "/" to normalize URL paths$addFields before matching or grouping$ltrim or $trim when both ends need work$rtrim to remove leading spaces (use $ltrim or $trim)$rtrim as a pipeline stage — it is an expression operatornull input returns nullchars with a single suffix string — it is a character set$toString first if needed$rtrimUse these points when cleaning strings in MongoDB.
End of string.
PurposeField or literal.
SyntaxCustom strip set.
OptionsRight vs left.
CompareURLs & imports.
Use caseMove on to $sampleRate for probabilistic sampling, or review $ltrim for leading character cleanup.
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