Custom Properties: Calculate new properties on the fly

Free plan users can create custom properties locally within a report. Growth and Enterprise plan users can save the custom properties globally to reuse in other reports. See our pricing page for more details.

Overview

Custom properties let you combine existing properties into new properties on the fly, using a simple Excel-like formula language. You can then use these new properties almost anywhere that you can use regular properties, with the ability to save/share them for reuse across your team. For more on why we built this, check out our blog.

Creating a Custom Property

1. Click the plus button to the right of the search bar, then select either “Custom Event Property” or “Custom User Property” to open the property builder

   
2. Give your property a name

   
3. Click the formula bar to start defining the calculations to perform for your property

   If you’re new to this feature, we recommend starting with one of the examples. Click the Insert Example drop down to populate the box with a use-case specific custom property.

   When writing your formula, click Ctrl + Space to see a list of all the available functions and their descriptions. Type period (.) to open the menu for choosing an event/profile properties to add to the custom property definition.

   If you are creating a “Custom Event Property” both event and user profile properties will be available to select. If you are creating a “Custom Profile Property” only user profile properties will be available for use in the custom property.

   Note that the formula used to compose your custom property can’t be longer than 20,000 characters.

   

Saving and Reusing a Custom Property

Custom properties are local to the report by default when you select Apply. To save the custom property permanently for use in other reports and to make it usable by other project members, click Save. We recommend Applying the custom property and using it in your local analysis first, before saving and sharing, to reduce clutter in the project.

When you create custom properties and select Save as Custom Property, your created custom property will be private by default. You can also add a description at this stage, so you and your colleagues can know what the custom property is for. You can also decide to save the custom property and share that custom property with specific colleagues, teams, or the entire organization by clicking “Save and Share”:

Common Use Cases

Grouping Marketing Channels

If you’re a marketer, using Mixpanel to show the impact of various channels on acquisition, you might want to group your UTM Sources into higher level buckets. For example:

• Facebook, Instagram, Twitter → Social
• Google, Bing → Search
• Everything else → Organic

You can also use the Channel Classifier template in custom properties as a starting point.

Compute Properties Mathematically from Other Properties

If you have an e-commerce app, you can combine “price” and “quantity” properties into a “total price” property as follows:

Compute the Number of Days Between Two Date Properties

Use custom properties to compute the date/time difference between two date properties. You can also use the special “TODAY()” function to find the difference between a date property and the current date/time. This is ideal when you want to transform a “DateofBirth” property into “age” or a “Created” property into “days active since registration”.

A new custom property can be defined by taking into account the “Created” property and using the following transformation:

Compare Different Properties

Use custom properties to create a new property if two property values are the same.

For example:

A company wants to find out what percentage of purchases are being made by users who have changed countries since signing up.

They can create a custom property to determine whether the two country values are the same with this transformation:

Extract Domain from Email Address

Extract the domain of the email from an email address. You can parse out parts of a string after ”@” using the SPLIT function:

Query a List with an Index

Let’s say you have a list of recommendations as a property, and you’d like to parse out the first recommendation as another string property.

You can parse out the first delivery ID in a list property with several DeliveryIDs:

The same syntax works with objects.

Additional Examples

Below are more formulas for common transformations, covering date math, string parsing, URL handling, and working with lists of objects. You would have to adjust these to meet your use case. Click into any example to see the formula applied in a sample report.

It requires a Mixpanel account and being part of the Demo project to view the example reports.

Use Case	Formula	Explanation
Time difference in minutes between two date properties (e.g. Updated at & Created)	(NUMBER(Updated at) - NUMBER(Created)) / 60	Converts dates into Epoch time using NUMBER(), calculates the difference, then divides by 60 to get minutes.
Check if a URL parameter exists (e.g. ref=email)	IF("ref=email" IN Current URL, TRUE, FALSE)	Returns TRUE if the parameter exists in the URL, otherwise FALSE.
Combine two string properties (e.g. Name & Email)	Name + " - " + Email	Uses the + operator for string concatenation to join the two properties with " - " in between.
Years since a date (e.g. Date of Birth)	DATEDIF(Date of Birth, TODAY(), "Y")	Uses DATEDIF() to subtract two dates (TODAY() − Date of Birth) and return the difference in years.
Match a URL pattern against a specific structure	REGEX_MATCH(Current URL, "https://.*/example/blog/.*/one")	Returns TRUE if the URL starts with https://, followed by any domain, /example/blog/, any string, and /one. Otherwise FALSE.
Rename property values depending on the current value	IFS(Page Variant == "A", "First test", Page Variant == "B", "Second test", DEFINED(Page Variant), "Others")	Assigns a new string for each existing value. Unmatched values are classified as "Others".
Days since first event (e.g. within 365 days of First Seen)	DATEDIF(First Seen, Time, "D")	Uses DATEDIF() to return the difference between the first and queried event in days.
Extract the hour from an ISO date property	NUMBER(MID(STRING(Time), 12, 2))	Uses MID() to extract the hour, starting at index 12 for 2 characters.
Split events into time buckets (e.g. work shifts)	LET(X, NUMBER(MID(Time, 12, 2)), IFS(X >= 0 AND X < 6, "Dawn Shift", X >= 6 AND X < 11, "Morning Shift", X >= 11 AND X < 18, "Afternoon Shift", X >= 18 AND X < 24, "Night Shift"))	Uses LET() to assign the extracted hour to a variable, then groups it into a named shift.
Group by platform (Mobile vs. Desktop)	IFS(Operating System == "Android", "Mobile", Operating System == "iOS", "Mobile", Operating System == "Windows", "Desktop", Operating System == "Mac OS X", "Desktop", TRUE, Operating System)	Classifies known Operating System values into Mobile or Desktop groups.
Map “not set” to a different value (e.g. 0)	IF(DEFINED(cost), cost, 0)	DEFINED() checks if the property is defined; keeps the value if so, otherwise returns the default.
Event within X seconds/hours/days of a user date property	IF((NUMBER(Time) - NUMBER(Registration Date) >= 0) AND (NUMBER(Time) - NUMBER(Registration Date) <= 172800), TRUE, FALSE)	Converts both dates to numbers and checks if the difference is under 48 hours (172,800 seconds).
Filter events between an hour and minute (e.g. before 17:30)	LET(TIME_STR, SPLIT(STRING(Time), "T", 2), HOUR, NUMBER(LEFT(TIME_STR, 2)), MIN, NUMBER(MID(TIME_STR, 4, 2)), IF(HOUR < 17 OR (HOUR == 17 AND MIN <= 30), TRUE, FALSE))	Extracts the time string, then hour/minute, and checks if the timestamp falls before or at 17:30.
Sum a property in a list if another matches (e.g. sum Price where Category is sneakers)	SUM(MAP(X, cart, IF(X["Category"] == "sneakers", X["Price"], FALSE)))	Loops through the list; sums the Price value wherever Category equals sneakers.
Return a UTM parameter from the URL not automatically extracted	REGEX_REPLACE((REGEX_EXTRACT(Current URL, "utm_source=([^&]*)", 1)), "%20", " ")	Extracts the text following utm_source= up to the next &, then replaces encoded spaces (%20) with blank spaces.
Change the data type of a value in a list of objects (e.g. Price to string)	MAP(X, cart, STRING(X["Price"]))	Loops through the list of objects, converting each Price number value to a string.
Time difference in seconds across mixed units (seconds & milliseconds)	((NUMBER(Time Processed (UTC)) / 1000) - NUMBER(Time)) +/- (HOURS IN SECONDS)	Converts both dates to Epoch time, dividing the millisecond timestamp by 1000 to align units, then adjusts for the UTC/project timezone offset.

Borrowed Properties

Borrowed properties allow you to take a property from a prior event and automatically add it as a property on a future event without needing to explicitly track the property in the future event.

Use Cases:

• Use client-side properties to populate a property on a server-side event. Example: “purchase” event could be a server-side event, while the “product search” event is a client-side event.
• Track a single event property and apply it to subsequent events. Example: It may be hard to track whether every event has dark mode enabled. You would need to keep track of the state of dark mode, and then add a “dark mode” property to every event that you track. Using borrowed events, you can just track one event with a property that indicates whether dark mode has been enabled or not, and have subsequent events borrow the property from that event.

Each project can use up to 20 borrowed properties.

Creating Borrowed Properties

The following is a demonstration of Borrowed Properties using the E-Commerce demo project, which anyone with a Mixpanel account can access.

In this demonstration, we present an event called “Purchase Completed”, which lacks the event property “Search term”. To enable a breakdown by “Search term”, we apply the Borrowed Property feature, leveraging the property from another event called “Product Searched”.

1. Purchase Completed does not have “Search term”

   
2. Products Searched does have “Search term”

   
3. Create a custom event property

   
4. Add a borrowed property

   
5. Select an event to borrow from

   
6. Select the property to borrow

   

Borrowing Mechanics

Borrowed Properties capture the value from the most recent borrowed event.

We apply a seven-day lookback window, so the second event must occur within seven days of the first. If no first event exists within this window, the borrowed property is assigned the value (not set).

The video below demonstrates how to create a borrowed property.

Some key notes

• Borrowed property creation is limited to Admin & Owner Roles only
• A project can have a maximum of 20 borrowed properties. Hence, you are encouraged to only create borrowed properties useful to the larger team
• A borrowed property, once created, is like any other custom property. It can be accessed by all in the project, depending on permissions
• Borrowing of a property is strictly from the most recent event in the 7-day lookback window. To elaborate
  • Say on event “purchase”, you want to borrow property “search term” from an event “search product”. If there are multiple events “search product” before “purchase”, the property will be borrowed from the most recent “search product” event where the property is set.
  • Lookback is also fixed to a 7-day window. Say the “purchase” event occurred on 31st Jan, if the most recent “search product” occurred on 20th Jan, the borrow functionality will return “search term” = (not set), since this event happened 11 days ago, which is outside the lookback window range.

To use a borrowed property with other functions, you would need to:

1. Create a custom property with just the borrowed property on its own \
2. Create a separate custom property using the borrowed property (i.e., the 1st custom property) \
3. Here’s an example of a report with Searched Category custom property using Search term (Products Searched) borrowed property \

Reference

Functions

Use the following functions in the Formula field to modify your custom property:

Function	Definition	Syntax & Example
if	Evaluates if an expression is true or false.	if(condition, value if true, value if false) Example: if(A=="Facebook" or A=="Twitter", "Social", A)
ifs	Runs multiple checks and returns a value corresponding to the first true result. If no conditions are true, undefined is returned.	ifs(condition1, value1, condition2, value2, …) Example: ifs( A<60,"Less than 1 hour", A<120, "More than 1 hour but less than 2 hours", A>=120, "More than 2 hours")
not	Returns values that are not true.	not(condition) Example: not(A == "Facebook")
and	Returns true if both conditions are met. Else, returns false.	x and y Example: if(A=="San Francisco" and B=="Chrome", "Valid user", "Invalid User")
or	Returns true if either condition is met. Else, returns false.	x or y Example: if(A=="San Francisco" or B=="Chrome", "Valid user", "Invalid User")
in	Returns true if the first condition is contained in the second condition.	x in condition Example: if("Facebook" in A, "Facebook Corporation", A) This can also be used to check against a list of values: if(A in ["Chrome","Firefox","Edge"],"Acceptable browser","Unsupported browser")
boolean	Casts the argument to a boolean.	boolean(value)->false, boolean(alternate value)-> true Example: boolean(A)
number	Casts the argument to a number.	number(value to cast) Example: number(A)
string	Casts the argument to a string.	string(value to cast) Example: string(A)
defined	Determines if a value exists. If a property is not defined on a parent event or profile, this will return false, otherwise this will return true.	defined(variable to check for existence) Example: defined(A)
has_prefix	Determines whether a string starts with another string. This comparison is case-insensitive.	has_prefix(string to check, prefix) Example: has_prefix(A, "United")
has_suffix	Determines whether a string ends with another string. This comparison is case-insensitive.	has_suffix(string to check, suffix) Example: has_suffix(A,"States")
min	Determines the minimum value between two numbers.	min(number, number) Example: min(A,B)
max	Determines the maximum value between two numbers.	max(number, number) Example: max(A,B)
floor	Returns the largest integer that is smaller than or equal to the input (ie: rounds down to the nearest integer).	floor(number) Example: floor(A)
ceil	Returns the smallest integer value greater than or equal to the input (ie: rounds up to the nearest integer).	ceil(number) Example: ceil(A)
round	Returns the nearest integer value of the input value.	round(number) Example: round(A)
upper	Cast string property values to uppercase.	upper(string property) Example: upper(A); upper("hello") -> “HELLO”
lower	Cast string property values to lowercase.	lower(string property) Example: lower(A); lower("FacEBook") -> “facebook”
parse_url()	Extracts the part of the url that is specified: domain(google) or full_domain(google.co.uk)	parse_url(string property, “domain”) or parse_url(string property, “full_domain”) Example: parse_url(A,“domain”)
regex_extract	If haystack is a string and pattern matches at least one substring, extracts the result from the first pattern match in haystack. The result is a string equal to the entire regex match, or if a capture group is specified, only that portion of the match. We use the PCRE2 regex engine.	regex_extract(haystack, pattern, <optional capture group#>) Example: regex_extract("iPhone5.1","iPhone(...)",1) ->5.1
regex_match	Returns true if the pattern matches any part of the string. We use the PCRE2 regex engine.	regex_match(haystack, pattern) Example: regex_match("zzhaystackzz", "ha(..)ack") -> true // Use (?-i) for case-sensitive matching: regex_match("HAYSTACK", "(?-i)haystack") -> false
regex_replace	Replaces the parts of a string that match a regular expression with a different string. We use the PCRE2 regex engine.	regex_replace(haystack, pattern, replacement) Example: // convert currency string to number: regex_replace("$1,234,567", "[^.0-9]\*", "")) -> 1234567
datedif	Subtract two dates. Units: D: days. M: months. Y: years MD: days remaining after subtracting whole months. YM: months remaining after subtracting whole years. YD: days, assuming start_date and end_date are within 1 year. Use TODAY() for current day.	datedif(start_date,end_date,unit) Example: datedif(registration_date,TODAY(), "M") -> 5
len	Returns the length of the string or the list.	len(string) or len(list) Example: len("Canada") -> 6
left	Returns characters from the beginning of a given string.	left(string, num_of_characters) Example: left("Canada",3) -> “Can”
right	Returns characters from the end of a given string	right(string, num_of_characters) Example: right("Canada",3) -> “ada”
mid	Returns characters from the middle of a given string	mid(string, first_index, num_of_characters) Example: mid("Canada",1,4) -> “Cana”
split	Splits a string into different parts based on a user-specified delimiter, and lets you select a particular split. Delimiter must be a single ASCII character. To fetch a list of all splits, don’t pass a third argument. The first split is accessible by passing n=1 (second with n=2, …)	split(input string, delimiter, [n: optional]) → string Examples with 1 split: split("[e-mail]","@",2) -> “dm.com” split("[e-mail]","@",4) -> undefined split("[e-mail]","/",2) -> [e-mail] split("empty//string/","/",2) -> "" Examples with all splits: split("[e-mail]","@") -> [“dwight”, “dm.com”] split("a/b/c/d", "/") -> [“a”, “b”, “c”, “d”] split("a/b/c/d", "-") -> [“a/b/c/d”] split("a//b/c/d", "/") -> [“a”, "", “b”, “c”, “d”]
let	Define a variable and use it in an expression. This helps keep the custom property definition neat and non-repetitive. Variables are only active within the scope of the LET function. You can nest multiple let functions to define multiple variables.	let(name, definition, expression) // define a variable "spend" and use it in an expression let( spend, <price> * <quantity>, ifs( spend < 50, "no discount", spend < 200, "gold discount", spend > 200, "platinum discount", TRUE, "invalid" ) ) Note: <price> and <quantity> are event properties.
any	Evaluates to TRUE if the given expression is true for any value in the given list. The expression can refer to the current list element by the given name.	any(name, list, expr) Example: Let’s say you had a list of numbers called priceList= [5,205,178,12,22] any(X, priceList, X > 300) -> false. any(X, priceList, X >= 5 and X < 300) -> true.
all	Evaluates to TRUE if the given expression is true for all values in the given list. The expression can refer to the current list element by the given name.	all(name, list, expr) Example: Let’s say you had a list of numbers called priceList= [5,205,178,12,22] all(X, priceList, X > 5 and X < 200) -> false. all(X, priceList, X >= 5 and X < 300) -> true.
filter	Filters the given list to only include items for which the given expression is true. The expression can refer to the current list element by the given name.	filter(name, list, expr) Example: Let’s say you had a list of numbers called priceList= [5,205,178,12,22] filter(X, priceList, X>100) -> new shortened list = [205,178]
map	Transforms each value in the given list using the given expression. The expression can refer to the current list element by the given name.	map(name, list, expr) Example: Let’s say you had a list of states = [“Georgia”,“Florida”,“Texas”] map(X, states, lower(X)) -> [“georgia”,“florida”,“texas”]
sum	Sums all numbers in the given list. Non-numeric items in the list are ignored.	sum(list) Example: Let’s say you had a list of numbers called priceList= [5,205,178,12,22] sum(priceList) -> 422. sum(filter(X, priceList, X>100)) -> 383, because filter(X,priceList, X>100) -> [205,178] and sum([205,178]) -> 383.

Numeric Operators

Use the following numeric operators in the Formula field to modify your custom property using:

• +: Addition. Operator can also be used to create string concatenation, for example: "string_to_concatenate" + your string property
• -: Subtraction
• *: Multiplication
• /: Division
• %: Modulo

Comparison Operators

Use the following comparison operators in the Formula field to modify your custom property:

• <: The first number is strictly less than the second number.
• >: The first number is strictly greater than the second number.
• >=: The first number is greater than or equal to the second number.
• <=: The first number is less than or equal to the second number.
• ==: The first argument is equal to the second argument. If both arguments are strings, the comparison is case-insensitive.
• !=: The first argument is not equal to the second argument. If both arguments are strings, the comparison is case-insensitive.

Constants

• false: Represents the literal value of boolean false.
• true: Represents the literal value of boolean true.
• undefined: Represents the literal value of cases that aren’t defined.