This is based on the superb work by Mohit Bhoite
Install the arduino example File -> Examples -> ArduinoISP -> ArduinoISP
I'm programming the ATTiny85 (ATTINY85V-10PU-ND) using an Arduino UNO... and that is actually a bit of a pain! There are quite a few online tutorials however most of them seem out of date or broken because of updates to the Arduino IDE / ssl certificates at the moment.
Here my current setup 26 December 2023
- Arduino IDE 2.2.1
- https://github.com/SpenceKonde/ATTinyCore
In order to install the ATTinyCore board configuration I needed to follow the details in this comment
Thankfully the ATTinyCore configuration does not require you to have a 10 micro-farad capacitor like these instructions
Pin out guide for ATTiny85:
Wiring setup:
| Arduino | ATtiny85 |
|---|---|
| GND | GND |
| 3.3v | VCC (chip pin 8) |
| ~10 | Pin 5 (chip pin 1) |
| 13 | Pin 2 (chip pin 7) |
| 12 | Pin 1 (chip pin 6) |
| 11 | Pin 0 (chip pin 5) |
When flashing the chip make sure to flash using the INTERNAL clock source. Otherwise the chip requires an external crystal oscillator and you cannot re-flash the chip without one.
These are the settings I'm using at the moment:
Then it is just about pressing Tools -> Burn Bootloader
This one was also really annoying! there is a handy upload button 
but it does not work!
To upload your program you need to navigate to sketch -> Upload using programmer
After that I've still found it hit and miss to successfully upload the program with weird intermittent issues but it works well enough...