Breaking changes:

• Fixing maxBodyLength enforcement (#3786)
• Don't rely on strict mode behaviour for arguments (#3470)
• Adding error handling when missing url (#3791)
• Update isAbsoluteURL.js removing escaping of non-special characters (#3809)
• Use native Array.isArray() in utils.js (#3836)
• Adding error handling inside stream end callback (#3967)

Fixes and Functionality:

• Added aborted even handler (#3916)
• Header types expanded allowing boolean and number types (#4144)
• Fix cancel signature allowing cancel message to be undefined (#3153)
• Updated type checks to be formulated better (#3342)
• Avoid unnecessary buffer allocations (#3321)
• Adding a socket handler to keep TCP connection live when processing long living requests (#3422)
• Added toFormData helper function (#3757)
• Adding responseEncoding prop type in AxiosRequestConfig (#3918)

Internal and Tests:

• Adding axios-test-instance to ecosystem (#3786)
• Optimize the logic of isAxiosError (#3546)
• Add tests and documentation to display how multiple inceptors work (#3564)
• Updating follow-redirects to version 1.14.7 (#4379)

Documentation:

• Fixing changelog to show corrext pull request (#4219)
• Update upgrade guide for https proxy setting (#3604)

Huge thanks to everyone who contributed to this release via code (authors listed below) or via reviews and triaging on GitHub:

• Jay
• Rijk van Zanten
• Kohta Ito
• Brandon Faulkner
• Stefano Magni
• enofan
• Andrey Pechkurov
• Doowonee
• Emil Broman
• Remco Haszing
• Black-Hole
• Wolfram Kriesing
• Andrew Ovens
• Paulo Renato
• Ben Carp
• Hirotaka Tagawa
• 狼族小狈
• C. Lewis
• Felipe Carvalho
• Daniel
• Gustavo Sales