Upgrade Firmware

1. Backup all your data on your nexus 5 as flashing this official firmware might result in data loss.
2. Charge your handset to at least 80% so that flashing goes well without any issues due to low battery.
3. You must have installed adb or minimal fastboot on your computer.
4. Download the developer preview for hammerhead on your computer.
5. Download and install win zip for any standard extractor tool on your computer.
6. This method can also be used on other nexus devices like nexus 6 shamu, nexus 9 volantis.

Install Android marshmallow on Nexus 5 hammerhead:

• System ui tuner: This is new feature that let you tweak ui a bit but has been hidden just like developer option.If you want to add it to setting app,swipe down the notification panel and on top you will notice a gear icon.Press and hold it and you will notice that it starts spinning.Just leave it once you notice the vigorous spin and you will see a toast message "system ui tuner" added to settings.
• There are ton of brand new wallpapers.
• Google launcher now has vertical scrolling instead of horizontal.
• Multi window: Google finally introduced multi window concept in tablet version of os.You can run two apps in a single window.Activating multi window is also too easy.When you open recents you will notice there is another option beside the closing button on cards.Press on it and activate multi window.But this multi window is not configurable which means adjust width of apps that are running.
• Phone short cut on lock screen is replaced with google now.
• Search bar in settings menu.
• New volume panel: You can now adjust volume of media, call and notification from single window .This feature is absent in previous versions of android though present in most of the oem provided firmwares.
• Auto rotation on home screen is also added which you can find in launcher settings.
• Now on tap: If you use google now frequently this feature might help you a lot.Usually when you press and hold on home button it will take you to google now.If you enable this feature when you try to access google now on any app it load some related suggestions along with some google now card.
• Screen shot notification will also have delete button along with share option.
• Memory option: This is available in settings .It gives you memory usage on your device from last "3hrs or 6 hrs or 1 day".
• App permission manger is the major thing in android m.This lets you to block certain permission so that the app cannot access them.like if you don't want facebook to access your bluetooth you can now do it with out rooting your device,

• Unlocking bootloader is the first step that you have to go through before installing android m on your nexus 5.But unlocking will erase all the data on your device so have a backup first before proceeding further.
• Download and install lg device drivers on your computer.
• Come back to phone and press and hold power button and choose power off.
• Hold volume up, down button and power button simultaneously and you will notice that your device goes into fastboot mode.At this stage connect to computer using usb cable.
• Once you are in fastboot mode connect your nexus 5 device to computer through usb cable and if you notice any driver installation process let it complete first.
• Download  fastboot on our laptop or Pc and install it.You can install it any location but choose location as c: which is default location.
• open the fastboot folder which is located in "c:\programming files".Right click on empty space by holding shift and you see an option "open cmd here".
• If you don't find this option then press windows and R buttons at same time ,Run pops up and type cmd to open command prompt.
• Now go to fastboot folder and copy the location of it which you can see in address bar of folder.
• In command prompt type the command "Cd location of fastboot folder" and press enter.You will notice that fastboot appears in command line.To paste location right click on empty space in cmd and several pops up.Select paste.
• One you press enter you have to notice minimal adb and fastboot in command line instead of c or some thing.
• Once you are in fastboot window type "fastboot devices" and press enter.If your device is detected you will get a serial number in list of  devices attached.If not uninstall drivers and install them again.
• Now type the command "fastboot oem unlock" and press enter and you will get a prompt on your nexus 5 if you want to unlock your handset.Click on yes and this will erase all your data or info on device.It reboots again after unlocking.
• Download android m developer file on your computer and extract it using 7zip or winzip.
• The extracted file will have flash-all.bat file along with all other imgs like bootloader ,system ,recovery,boot and all.
• If you don't find all images and if you see another folder that contain all other images cut then from that folder and paste it in the parent folder.
• Now double click on flash-all.bat file and it flashes all the files for you.Once the process is completed you will have android m installed on your nexus 5.
•  If flash-all.bat file failed to installed then you have to flash the image files manually.
• Copy all the image files from the extracted folder and place them in fastboot folder.Put your nexus 5 in fastboot mode again and follow the process.
• Now type the command "fastboot flash bootloader bootloader.img" (here this green underlined word indicates the name of the bootloader file.It may not be exact word.You have to type the name which you can see in the fastboot folder)
• Once the bootloader is flashed reboot it bootloader again by typing "fastboot reboot bootloader".
• Now type the command "fastboot flash radio radio-filename.img" and hit enter.Once it is flashed reboot to bootloader again.
• Now type the command "fastboot flash system system.img" and dont reboot to bootloader this time.
• Now type "fastboot flash userdata userdata.img" once flashed just continue to next command.
• Now type the command "fastboot flash boot boot.img".
• Now type the command "fastboot flash recovery recovery.img".
• Now erase cache using the command "fastboot erase cache" and flash cache img too using the command "fastboot flash cache cache.img".
• Now type the last command which reboot your nexus 5.Type "fastboot reboot" and hit enter.You will notice that the your device reboots.

• Charge your Lg Nexus 5 to at least 80% .
• Backup all your apps and data on your device to external sdcard or computer as flashing resurrection remix rom will erase all the app data on your device including contacts.
• Enable usb debugging on your Lg nexus 5.Of course you don't need to do this for sure but enable it.
• Download resurrection remix rom and gapps if you need them.Transfer them to your device internal storage
• Backup Efs and modem partitions of your Lg nexus 5..
• You must have Clockworkmod recovery installed on your phone.

Install resurrection remix custom rom on Lg nexus 5:

• Theme engine: Theme engine is from the cyanogenmod custom rom which basically changes the look user interface from lock screen  to ring tones all the way up to boot animations.The speciality of the theme engine is the ability to choose individual elements of every theme you have installed.So you like the ring tons and wallpapers of one theme and icons of other theme then you can have them at a time.Just open the theme chooser and you will understand how to do it.
• Software Updates: Cyanogenmod rom is usually available in three types one is nightlies which gets updated with new features every night and are quite stable for daily usage.second one is the snapchat which is monthly build version which will be stable version and other one is the release candidate.Some times nightlies are considered must stable than the snapshots. 
• Status bar Tweaks:Status bar has lot of tweaks which include a brightness slider.Slide in status bar to adjust brightness of the screen.Double tap on status bar to sleep device and also network speed indicator for on going traffic info.
• If you root apps don't work then that is no response form super user it means it has been disabled and you can enable it in developer options easily.
• System ui tuner: This is new feature that let you tweak ui a bit but has been hidden just like developer option.If you want to add it to setting app,swipe down the notification panel and on top you will notice a gear icon.Press and hold it and you will notice that it starts spinning.Just leave it once you notice the vigorous spin and you will see a toast message "system ui tuner" added to settings.
• There are ton of brand new wallpapers.
• Google launcher now has vertical scrolling instead of horizontal.
• Multi window: Google finally introduced multi window concept in tablet version of os.You can run two apps in a single window.Activating multi window is also too easy.When you open recents you will notice there is another option beside the closing button on cards.Press on it and activate multi window.But this multi window is not configurable which means adjust width of apps that are running.
• Auto rotation on home screen is also added which you can find in launcher settings.
• Now on tap: If you use google now frequently this feature might help you a lot.Usually when you press and hold on home button it will take you to google now.If you enable this feature when you try to access google now on any app it load some related suggestions along with some google now card.
• Screen shot notification will also have delete button along with share option.
• Memory option: This is available in settings .It gives you memory usage on your device from last "3hrs or 6 hrs or 1 day".
• App permission manger is the major thing in android m.This lets you to block certain permission so that the app cannot access them.like if you don't want facebook to access your bluetooth you can now do it with out rooting your device.
• Phone short cut on lock screen is replaced with google now.
• Search bar in settings menu.
• New volume panel: You can now adjust volume of media, call and notification from single window .This feature is absent in previous versions of android though present in most of the oem provided firmwares.

1.Cyanogenmod custom rom nexus 5:

2.Blisspop rom for nexus 5:

3.Euphoria os rom nexus 5:

• Theme engine: It comes with a cyanogenmod mod theme engine so you can play with lot of themes.This is a great way of customizing your android device. You can theme each and every element of user interface all the way from wallpapers to boot animations.There are lot of themes available in playstore and some are premium too.
• Heads up notification: This notification system is similar to that in google'e one.Swipe left to dismiss notification and right to put it in background.Swiping down on it will open notification drawer and it merges in it.
• Wake options: Depending on the device you will have double tap to wake the device option in display settings and of course you have the option to put the device into sleep by double tapping on status bar.There is a option to wake phone after connecting charger.
• Animations: You can have custom animations for app opening and closing or while scrolling.
• Navigation: Besides device wake options you can even adjust dimensions of navigation bar and set custom actions too like long pressing  back button to kill recent app.In landscape mode navigation goes left hand side and yeah there is an option to disable this too if you don't like it.
• Security:  Privacy guard is available in this Rom along with blacklisting of calls and messages.
• Sound: AudioFx is available for better quality of music.Other features include increasing volume ring tone,profiles,less notifications,you can disable volume adjustable sound,separate ring tones and notifications volume as usual.
• Power: Advance reboot option is enabled by default so you can boot into recovery,fast boot,soft boot easily.
• Screen recorder: There is screen recorder option too in display settings to record your actions on your device.
• Quick settings panel is customizable and brightness control too is available.

These are noticeable features of euphoria OS Rom and there  are lot of other features too which you can explore on your own by flashing this custom Rom on Nexus 5.
Download  Euphoria os nexus 5 hammerhead 

4.Aicp Custom rom for nexus 5:

Aicp is one the best custom Roms available in android development .Aicp stands for android ice cold project.Initially this custom Roms used android open kang project as a base (Aokp in short) but they later moved to cyanogenmod Rom as aokp stopped updating its sources.So you can expect all features of cyanogenmod Rom in Aicp with some extra features too.They too have official support for nexus 5 hammerhead.

Features of aicp rom:

• Theme engine: Theme engine is from the cyanogenmod custom Rom which basically changes the look user interface from lock screen  to ring tones all the way up to boot animations.The speciality of the theme engine is the ability to choose individual elements of every theme you have installed.So you like the ring tons and wallpapers of one theme and icons of other theme then you can have them at a time.Just open the theme chooser and you will understand how to do it.


• Performance control:A default CPU manager app to control frequencies and governors.You can adjust CPU frequencies and also set them on boot too.
• Trebuchet: This is the default launcher that ships with cyanogenmod Rom.But if you flash gapps then you might loose this.It doesn't have too many features like nova or other launchers but its simple and fast.
• Status bar Tweaks:Status bar has lot of tweaks which include a brightness slider.Slide in status bar to adjust brightness of the screen.Double tap on status bar to sleep device and also network speed indicator for on going traffic info.
• Gesture anywhere:Gesture any where is also available which  makes it easy for you to launch apps with gestures instead of returning to home screen and app drawer to launch apps.
• App circle:In addition to this app circle bar is also present which makes it too easy to launch apps with just a swipe from the edge of the screen.
• Omni Switch: Omni Switch is an alternative for default recent window in android.To use this Open omni switch app from app drawer and set your preferred options.It opens a floating bubble just like facebook messenger and floats on every app and actions click on it to open your recent apps.

Download Aicp rom for nexus 5 hammerhead

5.Liquid smooth rom for nexus 5:

This rom is based on android open source project(aosp).This rom is light,fast, stable, smooth .They accepts feature requests too.So if you need a feature ti be present in this rom then you can actually request them to add in this rom.Its feature rich rom too.Guess what they too officially support hammerhead.All the features are working fine on nexus 5.

Features:

• Interface: This includes animations control.Clock and weather widgets are completely customizable so you don't need to download any separate app for both clock and weather widgets.
• Lock screen: You can customize weather widget on lock screen and double tapping on lock screen ring will put the device to sleep.
• Gesture anywhere: this feature is now quite common in most of the roms.Its a great way of navigation through gestures.
•  App circle bar:  YOu can access this by swiping from left or right edge of the screen and a tab appears with apps in it.You can launch your favourite apps easily with this feature and of cource you can disable it if you don't like.
• Notification lights: If your device supports notification led light then you can customize it.You can change the color of your led light for different actions.
• Heads up: When ever you receive a notification a rectangular bar with notification info will be displayed on top portion of the screen giving you a glimpse of what notification you have received this is called heads up notification and is common in android lollipop.You can adjust time for heads up to be displayed.
• Traffic indicator is also present in this rom for on going upload and download speeds which is displayed on your status bar.
• Double tapping on status bar will put the device to sleep.
• Brightness control: You can easily adjust screen brightness by just swiping on status bar.
• Status bar: Carrie label can be displayed on status bar and you can customize it too.Battery icon can also be changed if you don't like it.
• Ad blocker is present in this rom by default and it takes care of ads showing up in your browser or apps.
• Layers: This is an alternative to cyanogenmod theme engine and you can customize ui using themes.
• Performance control:  This lets you to control your cpu behavior.You can play with frequencies,schedulers,governors etc.So you don't need to go for any other cpu control apps.
• and lot more features............

Download liquid smooth for nexus 5 hammerhead

This completes the list of best lollipop custom roms for Nexus 5 hammerhead.If you think that the list is incomplete then please let us know which rom are you using on your nexus 5 and why is it the best rom for you.Remember that choosing the best rom is always a personal preference.