diff --git a/_data/links_en.yml b/_data/links_en.yml
index 579b956..56b6564 100644
--- a/_data/links_en.yml
+++ b/_data/links_en.yml
@@ -59,24 +59,28 @@
   num:   13
   link:  chapters/hud.html
 
+- title: "SFINV: Inventory Formspec"
+  num:   14
+  link:  chapters/sfinv.html
+
 - hr: true
 
 - title: ItemStacks
-  num:   14
+  num:   15
   link:  chapters/itemstacks.html
 
 - title: Inventories
-  num:   15
+  num:   16
   link:  chapters/inventories.html
 
 - hr: true
 
 - title: Releasing a Mod
-  num: 16
+  num: 17
   link: chapters/releasing.html
 
 - title: Read More
-  num: 17
+  num: 18
   link: chapters/readmore.html
 
 - hr: true
diff --git a/en/chapters/sfinv.md b/en/chapters/sfinv.md
new file mode 100644
index 0000000..54c6a91
--- /dev/null
+++ b/en/chapters/sfinv.md
@@ -0,0 +1,236 @@
+---
+title: "SFINV: Inventory Formspec"
+layout: default
+root: ../../
+---
+
+## Introduction
+
+Simple Fast Inventory (SFINV) is a mod found in Minetest Game that is used to
+create the player's inventory [formspec](formspecs.html). SFINV comes with
+an API that allows you to add and otherwise manage the pages shown.
+
+Whilst SFINV by default shows pages as tabs, pages are called "pages" as
+it's entirely possible that a mod or subgame decides to show them in
+some other format instead.
+
+* [Registering a Page](#registering-a-page)
+    * [A more complex example](#a-more-complex-example)
+* [Receiving events](#receiving-events)
+* [Conditionally showing to players](#conditionally-showing-to-players)
+* [on_enter and on_leave callbacks](#on_enter-and-on_leave-callbacks)
+
+## Registering a Page
+
+So, to register a page you need to call the aptly named `sfinv.register_page`
+function with the page's name, and its definition. Here is a minimal example:
+
+{% highlight lua %}
+sfinv.register_page("mymod:hello", {
+    title = "Hello!",
+    get = function(self, player, context)
+        -- TODO: implement this
+    end
+})
+{% endhighlight %}
+
+You can also override an existing page using `sfinv.override_page`.
+
+If you ran the above code and clicked the page's tab, it would probably crash
+as sfinv is expecting a response from the `get` method. So let's add a response
+to fix that:
+
+{% highlight lua %}
+sfinv.register_page("mymod:hello", {
+    title = "Hello!",
+    get = function(self, player, context)
+        return sfinv.make_formspec(player, context,
+                "label[0.1,0.1;Hello world!]", true)
+    end
+})
+{% endhighlight %}
+
+The `make_formspec` function surrounds your formspec with sfinv's formspec code.
+The fourth parameter, currently set as `true`, determines whether or not the
+player's inventory is shown.
+
+<figure>
+    <img src="{{ page.root }}/static/sfinv_hello_world.png" alt="Furnace Inventory">
+    <figcaption>
+        Your first sfinv page! Not exactly very exciting, though.
+    </figcaption>
+</figure>
+
+### A more complex example
+
+Let's make things more exciting. Here is the code for the formspec generation
+part of a player admin tab. This tab will allow admins to kick or ban players by
+selecting them in a list and clicking a button.
+
+{% highlight lua %}
+sfinv.register_page("myadmin:myadmin", {
+    title = "Tab",
+    get = function(self, player, context)
+        local players = {}
+        context.myadmin_players = players
+
+        -- Using an array to build a formspec is considerably faster
+        local formspec = {
+            "textlist[0.1,0.1;7.8,3;playerlist;"
+        }
+
+        -- Add all players to the text list, and to the players list
+        local is_first = true
+        for _ , player in pairs(minetest.get_connected_players()) do
+            local player_name = player:get_player_name()
+            players[#players + 1] = player_name
+            if not is_first then
+                formspec[#formspec + 1] = ","
+            end
+            formspec[#formspec + 1] = minetest.formspec_escape(player_name)
+            is_first = false
+        end
+        formspec[#formspec + 1] = "]"
+
+        -- Add buttons
+        formspec[#formspec + 1] = "button[0.1,3.3;2,1;kick;Kick]"
+        formspec[#formspec + 1] = "button[2.1,3.3;2,1;ban;Kick + Ban]"
+
+        -- Wrap the formspec in sfinv's layout (ie: adds the tabs and background)
+        return sfinv.make_formspec(player, context,
+                table.concat(formspec, ""), false)
+    end,
+})
+{% endhighlight %}
+
+There's nothing new about the above code, all the concepts are covered above and
+in previous chapters.
+
+<figure>
+    <img src="{{ page.root }}/static/sfinv_admin_fs.png" alt="Player Admin Page">
+    <figcaption>
+        The player admin page created above.
+    </figcaption>
+</figure>
+
+## Receiving events
+
+You can receive formspec events by adding a `on_player_receive_fields` function
+to a sfinv definition.
+
+{% highlight lua %}
+on_player_receive_fields = function(self, player, context, fields)
+    -- TODO: implement this
+end,
+{% endhighlight %}
+
+Fields is the exact same as the fields given to the subscribers of
+`minetest.register_on_player_receive_fields`. The return value of
+`on_player_receive_fields` is the same as a normal player receive fields.
+Please note that sfinv will consume events relevant to itself, such as
+navigation tab events, so you won't receive them in this callback.
+
+Now let's implement the `on_player_receive_fields` for our admin mod:
+
+{% highlight lua %}
+on_player_receive_fields = function(self, player, context, fields)
+    -- text list event,  check event type and set index if selection changed
+    if fields.playerlist then
+        local event = minetest.explode_textlist_event(fields.playerlist)
+        if event.type == "CHG" then
+            context.myadmin_selected_idx = event.index
+        end
+
+    -- Kick button was pressed
+    elseif fields.kick then
+        local player_name = context.myadmin_players[context.myadmin_selected_idx]
+        if player_name then
+            minetest.chat_send_player(player:get_player_name(),
+                    "Kicked " .. player_name)
+            minetest.kick_player(player_name)
+        end
+
+    -- Ban button was pressed
+    elseif fields.ban then
+        local player_name = context.myadmin_players[context.myadmin_selected_idx]
+        if player_name then
+            minetest.chat_send_player(player:get_player_name(),
+                    "Banned " .. player_name)
+            minetest.ban_player(player_name)
+            minetest.kick_player(player_name, "Banned")
+        end
+    end
+end,
+{% endhighlight %}
+
+There's a rather large problem with this, however. Anyone can kick or ban players! You
+need a way to only show this to players with the kick or ban privileges.
+Luckily SFINV allows you to do this!
+
+## Conditionally showing to players
+
+You can add an `is_in_nav` function to your page's definition if you'd like to
+control when the page is shown:
+
+{% highlight lua %}
+is_in_nav = function(self, player, context)
+    local privs = player:get_privs()
+    return privs.kick or privs.ban
+end,
+{% endhighlight %}
+
+Note the the `is_in_nav` is only called when the player's inventory formspec is
+generated. This happens when a player joins the game, switches tabs, or a mod
+requests it using SFINV's API.
+
+This means that you need to manually request that SFINV regenerates the inventory
+formspec on any events that may change `is_in_nav`'s result. In our case,
+we need to do that whenever kick or ban is granted or revoked to a player:
+
+{% highlight lua %}
+local function on_grant_revoke(grantee, granter, priv)
+    if priv == "kick" or priv == "ban" then
+        local player = mientest.get_player_by_name(grantee)
+        if player then
+            sfinv.set_player_inventory_formspec(player)
+        end
+    end
+end
+
+-- Check that the function exists, in order to support older Minetest versions
+if minetest.register_on_priv_grant then
+    minetest.register_on_priv_grant(on_grant_revoke)
+    minetest.register_on_priv_revoke(on_grant_revoke)
+end
+{% endhighlight %}
+
+## on_enter and on_leave callbacks
+
+You can run code when a player enters (your tab becomes selected) or
+leaves (another tab is about to be selected) your tab.
+
+Please note that you can't cancel these, as it would be a bad user experience
+if you could.
+
+Also note that the inventory may not be visible at the time
+these callbacks are called. For example, on_enter is called for the home page
+when a player joins the game even before they open their inventory!
+
+{% highlight lua %}
+on_enter = function(self, player, context)
+
+end,
+
+on_leave = function(self, player, context)
+
+end,
+{% endhighlight %}
+
+## Adding to an existing page
+
+<div class="notice">
+    <h2>To Do</h2>
+
+    This section will be added soon&trade;.
+    This placeholder is just to let you know that it is possible!
+</div>
diff --git a/static/sfinv_admin_fs.png b/static/sfinv_admin_fs.png
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diff --git a/static/sfinv_hello_world.png b/static/sfinv_hello_world.png
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