Framework vs Library in software development: What is the difference?

The difference: framework and library explained simply and understandably

Software developmentUPDATED ON March 14, 2022

Cover image for blog post defining the difference between a library and framework in software development

In software development, in addition to programming languages, there are two other pillar technologies that are part of almost every software development process – frameworks and libraries. The two terms refer to different things and yet are very often interchanged with each other in the same context.

In this short article, we explain the difference between a framework and a library.

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What is a library?

In contrast to pure code, a library is not an independently executable unit, but an additional module that is requested by a programme.

To put it simply, libraries are collections of classes and functions, which is why they are sometimes also called component or class libraries. With the help of a programme interface (API / Application Programming Interface), access to the necessary functions from the library is made possible. However, access is only limited to the “public” functions; libraries also have “private” functions that work in the background but remain hidden from the outside world.

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The sections of code that libraries provide serve to speed up the development process of a software project and provide ready-made solutions to frequently occurring problems. Libraries help developers format code more efficiently and quickly than writing it from scratch as vanilla code.

Software development library metaphor

A library can be compared to the interior design of a house. The same four walls can be granularly customised with choices across paint or wallpaper, flooring, pieces of furniture and decoration. An interior designer doesn’t mix their own paint from chemicals and colourings or build a table from blocks of wood. All the elements combined to create the interior design of a space have been pre-made by someone else and just expertly arranged by the designer.

Similarly, a software developer using a library mixes and matches all the ready blocks of code provided by the library and can then customise them if they wish. Like an interior designer giving a piece of furniture a different coloured coat of paint so it better creates the effect they are aiming for.

What is a Framework?

A framework is a special kind of library that does not contain “finished” functions like a regular library. Frameworks are rather programme scaffolds that provide the blueprint but not the finished unit.

The framework, therefore, provides the blueprint and the basic framework and also shows what is still needed from the programmer in terms of customisation. The framework provides the flow of a software application and tells the developer what it needs and calls the code provided by the developer as required. If a library is used, the application calls the code from the library.

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Software development framework metaphor

You can think of a software development framework like the basic structure of a house including the support pillars and beams as well as central electrics and plumbing infrastructure.

The framework provides a core architecture that largely neutralises the potential for fundamental mistakes or inefficiencies – the wheel doesn’t have to be reinvented. But it also leaves plenty of freedom for customisation.

In our house metaphor, the builders or buyer would still be able to choose where internal walls should be placed, which room is used for what (as long as compatible with the framework eg. there may be some limitations where the bathroom can be to conveniently connect to plumbing) and fixtures and fittings.

The advantages of a framework are obvious: not only the increased efficiency but also the provision of an organisational basis is emphasised by many developers as a great advantage. The code is also well structured, but this also means that developers have less flexibility. The possible extensions to the programming therefore determine the possibilities of the framework.

Some frameworks offer more flexibility than others. For example, you might hear it said that the Angular framework is more “opinionated” than Vue.js, another JavaScript framework popular for frontend development. The more opinionated a framework, the less flexible it is. That has advantages and disadvantages.

More opinionated frameworks can be good for large, complex software applications as they help maintain consistency. However, that does come with the price of being able to customise the app with greater freedom.

Technically, frameworks are limited in their adaptability and the code must follow the rules and structures specific to the framework. This limits the developer’s freedom and flexibility but is not always the case. Less opinionated frameworks can offer developers a great deal of freedom.

Framework vs Library

The goal of frameworks and libraries is the same: to expand the range of out-of-the-box functions available to developers, optimising their workload and reducing room for error and inefficient code.  Frameworks and libraries are blocks of code developed by third parties that help solve common problems in a particular programming language.

However, there are technical differences between them. One core difference between a framework and a library is the use of queries. When using a library, the programmer decides when and where to call it.

When using a framework, the framework dictates that. It provides the basic framework and tells the programmer what is needed. Accordingly, the necessary code is inserted by the developer and supplements the framework according to the desired function. In the end, however, it is the framework that calls up the code when it needs it and is also responsible for the running of the programme.

The following diagram illustrates that core technical difference between how a framework and library work:

In summary

A library is a collection of functions developers can call at will and still control the flow of the software application. The operations performed to be performed by libraries are precisely and specifically defined.

A framework is a structure in which the application defines the content of the operation by asking the developer to fill in the spaces. The framework defines the concept with the functionality itself is defined by the developer with the end-user in mind.

Frameworks and libraries are code written by third parties to solve regular/common problems or to optimise performance. A key difference between the two is the inversion of control. When using a library, the control remains with the developer who tells the application when to call library functions. When using a framework, the control is reversed, which means that the framework tells the developer where code needs to be provided and calls it as it requires.

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