Savegames are located at:
C:\Users\[user]\AppData\LocalLow\Reflect Studios\Welcome To The Game
where [user] is name of system and C: is system drive where Widows OS is located at. (it's C: by default unless you changed it)

note: AppData is hidden folder means you need to go enable your system to show all folder both hidden and normal. To enable that go to My Computer, in top left corder click on "Organize" then find "Folder and search Options" and click on it. Window "Folder Options" will pop-up, go to tab "View" and move Radio Button in "Hidden files and folders" to "Show hidden files, folders, and drives". Click Apply then OK.

Start a new game, normal mode, then skip Adam call. In top right corner click on shutdown button, save progress and quit to main menu.

Save file created. This means every time you load this save game starts from day 2. And every time you load this save all codes and wiki links you find stays the same.

Exit game and backup this save. Save whole folder in e.g. My Documents.

First find wiki1 and wiki2 links.

The Deep Wiki I - contains code 1 and code 2
The Deep Wiki II - contains code 3 and code 4
The Deep Wiki III - contains code 5 and code 6

code 7 is randomly generated in one of these 3 wikis and code 8 will always be in "The Gatekeeper" (wiki 3)

Write down and actual paper what code you find (note: write it properly since you can easily mistake o and 0 or i and l). For these wiki links you can send them to a friend in chat box and every time you load new game just Alt+Tab(default Steam Overlay shortcut key).

If you want to maximum avoid threats, search for 1-2 codes, write them down, turn off the game and copy backup savefile to wttg folder. When turning on game just click continue game will start from day 2 and codes you find will be exactly the ones you need for Red Room. Now search rest of the codes.

My method i used is: found all codes from wiki 1 then turned off game copied save file, after loading i found all codes from wiki 2, then did same for wiki 3. Put all codes together and game is finished.

Repeat this method several times until you get all codes then but are in between http:// .ann.
Voilà game finished.

"Thankfully with the 2.0 update, Adam has added in a subtle visual cue that will tell you if a website has a code on it or not.

When you visit a website in-game, you will notice the blue loading bar going across the Address bar at the top of your browser. If this blue bar stays on-screen for an extra couple of seconds after the page has fully loaded, this means there is a Red Room code on the page."

i quote this guy who made guide "Welcome To The Game 2.0 Strategy Guide" https://gtm.steamproxy.vip/id/03051995

There is another tip i can give you for this method if you struggle finding the last few codes.
If you visit a 3 different pages with codes in it van will instantly spawn in front of your house. This means you load your save game, game recognize 0 pages with codes visited. Now visit 2 pages on purpose that you know for sure that have code in it (skip 8th code it won't count for this). Now click on page you suspect it has code then go look outside door for van if van is parked that page have 100% code in it. Do this until you find last one.

Another tip, special pages for "WHO AM I" secret ending CAN have code for Red Room. (personal experience)

By using this guide "REDRUM", "1337" and "DEEP WEB OUTLAW" achievements are easily obtainable.

After finishing game save file deletes but you backed up it. So if you want "WHERE AM I" achievement load again that save file. Open A.N.N. browser and copy this link
http://43eb90937b34e13b35e78f518f19f468.ann
now copy your Red Room link into this link and ENTER for secret ending.

For "THE DENIER", "THE DEVELOPER" and "THE CLOUD CHASER" you can download my save files from google drive. Copy them to your wttg directory. Go to Notes ingame and copy second link for Wiki 3, go to gatekeeper and fail answer on question. When hack starts you get achievement since i'm already master level on all 3 hacking mingames. Do this for all 3 types of hacks. You will save few hours of grinding by using my saves. You're welcome :steamhappy:
https://drive.google.com/open?id=1QE8HOvcx2emX5-5kdnFCDqDTI0zTVNj8

For "DEEP EXPLORER" you don't need to visit all active sites in single run. For me it just poped after finding 3rd code on my 5th or 6th game, but i think you need to visit sites taken down by government i'm not sure 100% about that. Also try to visit all links inside each website. I'm not sure about criteria of this achievement.