FileMaker Custom Functions

FileMaker Custom Functions

For many new developers, custom functions pose a challenge:  What are they, why do I need them, where do I find them, and how do I add them to FileMaker are just some of the questions. Another is recognizing when one is needed.  And let's not leave out the big one:  How do I write one of my own?

Why do I need Custom Functions?

FileMaker includes a long list of built-in functions, and adds more with every release.   But there is always a need to handle some particular type of problem one encounters when developing code for a client with specific needs.  Which is, pretty much, all of them.  So FileMaker added the ability to build your own.  You'll need FileMaker Pro Advanced to build your own, but only FileMaker Client to run them.

Finding Custom Functions

As for finding them, the biggest and oldest site is Brian Dunning's:  www.briandunning.com/filemaker-custom-functions/. With thousands of custom functions collected over the years, Dunning's site is the gold standard for FileMaker custom functions. Other options include FMFunctions.com, FileMaker Standards, Charles Ross,  and Jeremy Bante. the last three on GitHub.

If you use a Mac, download this free widget that shows the newest custom functions from Brian Dunning's site.  It also has a search function built in.

FileMaker Training offers their top ten custom functions a free downloadable file, and shows their use in this excellent video:

Making Your Own

Don't be afraid to jump right in and make your own.  There are plenty of helpful videos and blog posts to help you:

That last link above is about the Let command, an indispensable FileMaker function you'll want to master in order to write better custom functions.  Or to just be a better programmer.

Storing Custom Functions

You'll quickly find that storing FileMaker Custom Functions will become an issue.   And it is important:  what happens if one or more of the sites above go away and you didn't have all the functions you might need someday?  You can store them in your database, of course–it's not that hard to do.  But it takes time to add each one, and there are thousands  to add.

Matt Petrowsky is currently doing a multipart series on building a FileMaker database that finds and saves custom functions.  You'll need to sign up to his FileMaker Magazine service, but that is something you should do anyway.

Get Busy

You'll need custom functions sooner than you think, so don't waste time. Put some time aside to learn and to build your own list of favorite functions.


The weak can never forgive. Forgiveness is the attribute of the strong.

Mahatma Gandhi
Indian political and spiritual leader (1869 - 1948)

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