My name is Martin Fowler: I’m an author, speaker, and loud-mouth on the design of enterprise software. This site is dedicated to improving the profession of software development, with a focus on skills and techniques that will last a developer for most of their career. I’m the editor of the site and the most prolific writer. It was originally just my personal site, but over the last few years many colleagues have written excellent material that I’ve been happy to host here. I work for ThoughtWorks, a really rather good software delivery and consulting company. To find your way around this site, go to the intro guide.

News and Updates

My atom feed (RSS) announces any updates to this site, as well as various news about my activities and other things I think you may be interested in. I also make regular announcements via my twitter feed, which I copy to my facebook page.

Vote Against Trump

Tue 11 Oct 2016 15:59 EDT

In my writing, I don't usually get into US party politics. I have Opinions, but most political discussion quickly deteriorates into partisan bickering, which I find unsatisfying. But this presidential election is striking. Donald Trump is a demagogue who could do a lot of damage to both the US and the rest of the world. If you're an American who is undecided about who to vote for, or wishes to vote for a third party candidate, I feel I must explain why he is uniquely dangerous, and therefore why I it is necessary to vote for Mrs Clinton.


photostream 102

Sun 09 Oct 2016 11:25 EDT

Acadia N.P., ME

Evolutionary Database Design

Wed 28 Sep 2016 09:41 EDT

When we began to do agile software development at the turn of the century one of the big questions was how to evolve databases. In 2003 Pramod Sadalage and I published an article on the techniques we used, now we've updated this article to reflect a decade's worth of learning since then. The core techniques are still the same: organize database changes into composable migrations that capture schema refactorings and data updates. Store these migrations in the code repository and use tools to apply them to keep the database synchronized with the code.


photostream 101

Sun 18 Sep 2016 20:19 EDT

Helvellyn, Lake District, England

Basics of Web Application Security: Protect User Sessions

Mon 12 Sep 2016 10:40 EDT

Once you have a properly authenticated user, you also have a target for an attacker. If an attacker can infiltrate an authenticated session, he can do anything that user is allowed to do. So it's important to protect sessions by generating safe session identifiers, not exposing them, and managing the lifecycle of sessions.


Basics of Web Application Security: Authentication

Mon 15 Aug 2016 09:53 EDT

If we need to know the identity of our users, for example to control who receives specific content, we need to provide some form of authentication. Cade and Daniel explain the important, but often misunderstood, difference between authentication, authorization, and session management. They then help you understand your options for doing authentication safely.



Refactoring has become a core skill for software developers, it is the foundation behind evolutionary architecture and modern agile software development. I wrote the original book on refactoring in 2000, and it continues to be an interest of mine.

I’ve recently posted several essays on refactoring here:

  • JavaScript offers many targets for refactoring, so Refactoring a JavaScript Video Store takes the original video store example from the book and explores it in JavaScript. It outlines four directions you can take the refactoring: a nested function with a dispatcher, using classes, and transformation using an intermediate data structure.
  • While most of our logic is written directly in an imperative language, it is sometimes very useful to represent such logic in a data structure. Refactoring to an Adaptive Model describes this refactoring, which produces an adaptive model interpreted by generic code.
  • As a program grows in size it’s important to split it into modules, so that you don’t need to understand all of it to make a small modification. In Refactoring Module Dependencies I modularize a small example using layering and introducing Service Locator and Dependency Injection. I illustrate these using both Java and JavaScript so you can see how this modularization looks in different languages.
  • When I write code that deals with external services, I find it valuable to separate that access code into separate objects. Refactoring code that accesses external services shows how I would refactor some congealed code into a common pattern for this.
  • Modern languages give us the opportunity go beyond the loop as a way of handling repetitive behavior. Refactoring with Loops and Collection Pipelines provides a series of small examples of refactoring loops into my preferred approach.
  • Refactoring Code to Load a Document looks at how manipulating large JSON documents can often be made easier by encapsulating a combination of loading strategies.

TW logo

I discovered ThoughtWorks in 2000: then a small American company whose philosphy of software development was remarkably similar to my own. Now we’ve grown to around 4000 people world-wide, but kept the values that make us special. My colleagues have built critical systems for many clients in that time, and I’ve learned many lessons from them. While doing this, we found we often didn’t have the tools we needed, so we started to build them. This led to open-source tools such as CruiseControl, Selenium, Frank, and Moco as well as commercial products.

I have many opportunities, but I’ve stayed at ThoughtWorks because of the quality of my colleagues, who include both well-known speakers and those who may not be famous names but do an excellent job of software delivery (and feed me the information to write about). We are inspired by working with each other and our unusual three-pillar philosophy that raises professional excellence and social justice to the same level as financial performance.

And we are always looking for more great people to join our curious company. Maybe I’ll see you in one of our offices some day.

Continuous Integration and Delivery

For a long time I’ve been a champion of Continuous Integration which reduces integration risk by integrating early and often, an application of the principle of Frequency Reduces Difficulty. We’ve found CI to be a core technique at ThoughtWorks and use it almost all the time. At the heart of this is a style of development that minimizes long feature branches with techniques like Branch By Abstraction and Feature Toggles.

While this is useful, there was still risk present from software that works in the development environment to getting it to work in production. As a result we developed Deployment Pipelines to reduce this risk, moving closer to our aim of Continuous Delivery: building software in such a way that we confidently deploy the latest builds into production whenever there is a business need. We find this improves feedback, reduces risk, and increases the visibility of project progress.

For more information: take a look at my guide page on Continuous Delivery.

photo: Manuel Gomez Dardenne

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