diff --git a/6-backend-dev/4-exercise-tracker/.gitattributes b/6-backend-dev/4-exercise-tracker/.gitattributes
new file mode 100644
index 0000000..4891ee0
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/.gitattributes
@@ -0,0 +1,3 @@
+# Tell Linguist to exclude HTML files to help Replit language detection.
+*.html linguist-vendored
+*.css linguist-vendored
\ No newline at end of file
diff --git a/6-backend-dev/4-exercise-tracker/.gitignore b/6-backend-dev/4-exercise-tracker/.gitignore
new file mode 100644
index 0000000..97aca2e
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/.gitignore
@@ -0,0 +1,2 @@
+.env
+node_modules
\ No newline at end of file
diff --git a/6-backend-dev/4-exercise-tracker/.prettierignore b/6-backend-dev/4-exercise-tracker/.prettierignore
new file mode 100644
index 0000000..9736424
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/.prettierignore
@@ -0,0 +1 @@
+.replit
\ No newline at end of file
diff --git a/6-backend-dev/4-exercise-tracker/.replit b/6-backend-dev/4-exercise-tracker/.replit
new file mode 100644
index 0000000..f2f3406
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/.replit
@@ -0,0 +1,10 @@
+run = "npm start"
+entrypoint = "index.js"
+
+[packager]
+language = "nodejs"
+
+  [packager.features]
+  packageSearch = true
+  guessImports = true
+  enabledForHosting = false
\ No newline at end of file
diff --git a/6-backend-dev/4-exercise-tracker/README.md b/6-backend-dev/4-exercise-tracker/README.md
new file mode 100644
index 0000000..8ef1a56
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/README.md
@@ -0,0 +1,3 @@
+# Exercise Tracker
+
+This is the boilerplate for the Exercise Tracker project. Instructions for building your project can be found at https://www.freecodecamp.org/learn/apis-and-microservices/apis-and-microservices-projects/exercise-tracker
diff --git a/6-backend-dev/4-exercise-tracker/index.js b/6-backend-dev/4-exercise-tracker/index.js
new file mode 100644
index 0000000..859395f
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/index.js
@@ -0,0 +1,83 @@
+const express = require('express')
+const app = express()
+const cors = require('cors')
+require('dotenv').config()
+
+const users = [];
+
+function User(username, id) {
+    this.username = username;
+    this._id = id;
+    this.log = [];
+}
+
+users.push(new User('testUser', '0'))
+
+app.use(cors())
+app.use(express.static('public'))
+app.use(express.json()) // for parsing application/json
+app.use(express.urlencoded({ extended: true })) // for parsing application/x-www-form-urlencoded
+app.get('/', (req, res) => {
+    res.sendFile(__dirname + '/views/index.html')
+});
+
+app.route('/api/users')
+    .get((req, res) => {
+        res.json(users)
+    })
+    .post((req, res) => {
+        const id = users.length
+        const username = req.body.username
+        users.push(new User(username, id))
+        res.json({username: username, _id: id})
+    })
+
+app.post('/api/users/:_id/exercises', (req, res) => {
+    const description = req.body.description;
+    const duration = +req.body.duration;
+    const date = req.body.date;
+    const id = req.params._id;
+    const user = users[id]
+    if (!duration || !description){
+        return res.json({error: 'missing parameters'})
+    } else {
+        let dateString;
+        if (date) {
+            dateString = new Date(date).toDateString()
+        } else {
+            dateString = new Date().toDateString()
+        }
+
+        user.log.push({description: description, duration: duration, date: dateString});
+        user.count = user.log.length;
+        res.json({
+            username: user.username,
+            description: description,
+            duration: duration,
+            date: dateString,
+            _id: user._id
+        })
+    }
+})
+
+app.route('/api/users/:_id/logs')
+    .get((req, res) => {
+        const id = req.params._id;
+        const limit = Number(req.query.limit) || 0;
+        const response = users[id];
+        let newlog = response.log
+        if (req.query.from && req.query.to) {
+            const from = new Date(req.query.from).getTime();
+            const to = new Date(req.query.to).getTime();
+            newlog = newlog.filter(item => from <= new Date(item.date).getTime() <= to)}
+
+        if (limit > 0){
+            newlog = newlog.slice(0, limit)
+        }
+        response.log = newlog
+        res.json(response)
+    })
+
+const listener = app.listen(process.env.PORT || 3000, () => {
+    console.log('Your app is listening on port ' + listener.address().port)
+})
diff --git a/6-backend-dev/4-exercise-tracker/package-lock.json b/6-backend-dev/4-exercise-tracker/package-lock.json
new file mode 100644
index 0000000..89c50c2
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/package-lock.json
@@ -0,0 +1,749 @@
+{
+	"name": "fcc-exercise-tracker",
+	"version": "0.1.0",
+	"lockfileVersion": 2,
+	"requires": true,
+	"packages": {
+		"": {
+			"name": "fcc-exercise-tracker",
+			"version": "0.1.0",
+			"license": "MIT",
+			"dependencies": {
+				"cors": "^2.8.5",
+				"dotenv": "^8.2.0",
+				"express": "^4.16.4"
+			}
+		},
+		"node_modules/accepts": {
+			"version": "1.3.7",
+			"license": "MIT",
+			"dependencies": {
+				"mime-types": "~2.1.24",
+				"negotiator": "0.6.2"
+			},
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/array-flatten": {
+			"version": "1.1.1",
+			"license": "MIT"
+		},
+		"node_modules/body-parser": {
+			"version": "1.19.0",
+			"license": "MIT",
+			"dependencies": {
+				"bytes": "3.1.0",
+				"content-type": "~1.0.4",
+				"debug": "2.6.9",
+				"depd": "~1.1.2",
+				"http-errors": "1.7.2",
+				"iconv-lite": "0.4.24",
+				"on-finished": "~2.3.0",
+				"qs": "6.7.0",
+				"raw-body": "2.4.0",
+				"type-is": "~1.6.17"
+			},
+			"engines": {
+				"node": ">= 0.8"
+			}
+		},
+		"node_modules/bytes": {
+			"version": "3.1.0",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.8"
+			}
+		},
+		"node_modules/content-disposition": {
+			"version": "0.5.3",
+			"license": "MIT",
+			"dependencies": {
+				"safe-buffer": "5.1.2"
+			},
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/content-type": {
+			"version": "1.0.4",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/cookie": {
+			"version": "0.4.0",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/cookie-signature": {
+			"version": "1.0.6",
+			"license": "MIT"
+		},
+		"node_modules/cors": {
+			"version": "2.8.5",
+			"license": "MIT",
+			"dependencies": {
+				"object-assign": "^4",
+				"vary": "^1"
+			},
+			"engines": {
+				"node": ">= 0.10"
+			}
+		},
+		"node_modules/debug": {
+			"version": "2.6.9",
+			"license": "MIT",
+			"dependencies": {
+				"ms": "2.0.0"
+			}
+		},
+		"node_modules/depd": {
+			"version": "1.1.2",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/destroy": {
+			"version": "1.0.4",
+			"license": "MIT"
+		},
+		"node_modules/dotenv": {
+			"version": "8.2.0",
+			"license": "BSD-2-Clause",
+			"engines": {
+				"node": ">=8"
+			}
+		},
+		"node_modules/ee-first": {
+			"version": "1.1.1",
+			"license": "MIT"
+		},
+		"node_modules/encodeurl": {
+			"version": "1.0.2",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.8"
+			}
+		},
+		"node_modules/escape-html": {
+			"version": "1.0.3",
+			"license": "MIT"
+		},
+		"node_modules/etag": {
+			"version": "1.8.1",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/express": {
+			"version": "4.17.1",
+			"license": "MIT",
+			"dependencies": {
+				"accepts": "~1.3.7",
+				"array-flatten": "1.1.1",
+				"body-parser": "1.19.0",
+				"content-disposition": "0.5.3",
+				"content-type": "~1.0.4",
+				"cookie": "0.4.0",
+				"cookie-signature": "1.0.6",
+				"debug": "2.6.9",
+				"depd": "~1.1.2",
+				"encodeurl": "~1.0.2",
+				"escape-html": "~1.0.3",
+				"etag": "~1.8.1",
+				"finalhandler": "~1.1.2",
+				"fresh": "0.5.2",
+				"merge-descriptors": "1.0.1",
+				"methods": "~1.1.2",
+				"on-finished": "~2.3.0",
+				"parseurl": "~1.3.3",
+				"path-to-regexp": "0.1.7",
+				"proxy-addr": "~2.0.5",
+				"qs": "6.7.0",
+				"range-parser": "~1.2.1",
+				"safe-buffer": "5.1.2",
+				"send": "0.17.1",
+				"serve-static": "1.14.1",
+				"setprototypeof": "1.1.1",
+				"statuses": "~1.5.0",
+				"type-is": "~1.6.18",
+				"utils-merge": "1.0.1",
+				"vary": "~1.1.2"
+			},
+			"engines": {
+				"node": ">= 0.10.0"
+			}
+		},
+		"node_modules/finalhandler": {
+			"version": "1.1.2",
+			"license": "MIT",
+			"dependencies": {
+				"debug": "2.6.9",
+				"encodeurl": "~1.0.2",
+				"escape-html": "~1.0.3",
+				"on-finished": "~2.3.0",
+				"parseurl": "~1.3.3",
+				"statuses": "~1.5.0",
+				"unpipe": "~1.0.0"
+			},
+			"engines": {
+				"node": ">= 0.8"
+			}
+		},
+		"node_modules/forwarded": {
+			"version": "0.1.2",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/fresh": {
+			"version": "0.5.2",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/http-errors": {
+			"version": "1.7.2",
+			"license": "MIT",
+			"dependencies": {
+				"depd": "~1.1.2",
+				"inherits": "2.0.3",
+				"setprototypeof": "1.1.1",
+				"statuses": ">= 1.5.0 < 2",
+				"toidentifier": "1.0.0"
+			},
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/iconv-lite": {
+			"version": "0.4.24",
+			"license": "MIT",
+			"dependencies": {
+				"safer-buffer": ">= 2.1.2 < 3"
+			},
+			"engines": {
+				"node": ">=0.10.0"
+			}
+		},
+		"node_modules/inherits": {
+			"version": "2.0.3",
+			"license": "ISC"
+		},
+		"node_modules/ipaddr.js": {
+			"version": "1.9.1",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.10"
+			}
+		},
+		"node_modules/media-typer": {
+			"version": "0.3.0",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/merge-descriptors": {
+			"version": "1.0.1",
+			"license": "MIT"
+		},
+		"node_modules/methods": {
+			"version": "1.1.2",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/mime": {
+			"version": "1.6.0",
+			"license": "MIT",
+			"bin": {
+				"mime": "cli.js"
+			},
+			"engines": {
+				"node": ">=4"
+			}
+		},
+		"node_modules/mime-db": {
+			"version": "1.44.0",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/mime-types": {
+			"version": "2.1.27",
+			"license": "MIT",
+			"dependencies": {
+				"mime-db": "1.44.0"
+			},
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/ms": {
+			"version": "2.0.0",
+			"license": "MIT"
+		},
+		"node_modules/negotiator": {
+			"version": "0.6.2",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/object-assign": {
+			"version": "4.1.1",
+			"license": "MIT",
+			"engines": {
+				"node": ">=0.10.0"
+			}
+		},
+		"node_modules/on-finished": {
+			"version": "2.3.0",
+			"license": "MIT",
+			"dependencies": {
+				"ee-first": "1.1.1"
+			},
+			"engines": {
+				"node": ">= 0.8"
+			}
+		},
+		"node_modules/parseurl": {
+			"version": "1.3.3",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.8"
+			}
+		},
+		"node_modules/path-to-regexp": {
+			"version": "0.1.7",
+			"license": "MIT"
+		},
+		"node_modules/proxy-addr": {
+			"version": "2.0.6",
+			"license": "MIT",
+			"dependencies": {
+				"forwarded": "~0.1.2",
+				"ipaddr.js": "1.9.1"
+			},
+			"engines": {
+				"node": ">= 0.10"
+			}
+		},
+		"node_modules/qs": {
+			"version": "6.7.0",
+			"license": "BSD-3-Clause",
+			"engines": {
+				"node": ">=0.6"
+			}
+		},
+		"node_modules/range-parser": {
+			"version": "1.2.1",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/raw-body": {
+			"version": "2.4.0",
+			"license": "MIT",
+			"dependencies": {
+				"bytes": "3.1.0",
+				"http-errors": "1.7.2",
+				"iconv-lite": "0.4.24",
+				"unpipe": "1.0.0"
+			},
+			"engines": {
+				"node": ">= 0.8"
+			}
+		},
+		"node_modules/safe-buffer": {
+			"version": "5.1.2",
+			"license": "MIT"
+		},
+		"node_modules/safer-buffer": {
+			"version": "2.1.2",
+			"license": "MIT"
+		},
+		"node_modules/send": {
+			"version": "0.17.1",
+			"license": "MIT",
+			"dependencies": {
+				"debug": "2.6.9",
+				"depd": "~1.1.2",
+				"destroy": "~1.0.4",
+				"encodeurl": "~1.0.2",
+				"escape-html": "~1.0.3",
+				"etag": "~1.8.1",
+				"fresh": "0.5.2",
+				"http-errors": "~1.7.2",
+				"mime": "1.6.0",
+				"ms": "2.1.1",
+				"on-finished": "~2.3.0",
+				"range-parser": "~1.2.1",
+				"statuses": "~1.5.0"
+			},
+			"engines": {
+				"node": ">= 0.8.0"
+			}
+		},
+		"node_modules/send/node_modules/ms": {
+			"version": "2.1.1",
+			"license": "MIT"
+		},
+		"node_modules/serve-static": {
+			"version": "1.14.1",
+			"license": "MIT",
+			"dependencies": {
+				"encodeurl": "~1.0.2",
+				"escape-html": "~1.0.3",
+				"parseurl": "~1.3.3",
+				"send": "0.17.1"
+			},
+			"engines": {
+				"node": ">= 0.8.0"
+			}
+		},
+		"node_modules/setprototypeof": {
+			"version": "1.1.1",
+			"license": "ISC"
+		},
+		"node_modules/statuses": {
+			"version": "1.5.0",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/toidentifier": {
+			"version": "1.0.0",
+			"license": "MIT",
+			"engines": {
+				"node": ">=0.6"
+			}
+		},
+		"node_modules/type-is": {
+			"version": "1.6.18",
+			"license": "MIT",
+			"dependencies": {
+				"media-typer": "0.3.0",
+				"mime-types": "~2.1.24"
+			},
+			"engines": {
+				"node": ">= 0.6"
+			}
+		},
+		"node_modules/unpipe": {
+			"version": "1.0.0",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.8"
+			}
+		},
+		"node_modules/utils-merge": {
+			"version": "1.0.1",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.4.0"
+			}
+		},
+		"node_modules/vary": {
+			"version": "1.1.2",
+			"license": "MIT",
+			"engines": {
+				"node": ">= 0.8"
+			}
+		}
+	},
+	"dependencies": {
+		"accepts": {
+			"version": "1.3.7",
+			"requires": {
+				"mime-types": "~2.1.24",
+				"negotiator": "0.6.2"
+			}
+		},
+		"array-flatten": {
+			"version": "1.1.1"
+		},
+		"body-parser": {
+			"version": "1.19.0",
+			"requires": {
+				"bytes": "3.1.0",
+				"content-type": "~1.0.4",
+				"debug": "2.6.9",
+				"depd": "~1.1.2",
+				"http-errors": "1.7.2",
+				"iconv-lite": "0.4.24",
+				"on-finished": "~2.3.0",
+				"qs": "6.7.0",
+				"raw-body": "2.4.0",
+				"type-is": "~1.6.17"
+			}
+		},
+		"bytes": {
+			"version": "3.1.0"
+		},
+		"content-disposition": {
+			"version": "0.5.3",
+			"requires": {
+				"safe-buffer": "5.1.2"
+			}
+		},
+		"content-type": {
+			"version": "1.0.4"
+		},
+		"cookie": {
+			"version": "0.4.0"
+		},
+		"cookie-signature": {
+			"version": "1.0.6"
+		},
+		"cors": {
+			"version": "2.8.5",
+			"requires": {
+				"object-assign": "^4",
+				"vary": "^1"
+			}
+		},
+		"debug": {
+			"version": "2.6.9",
+			"requires": {
+				"ms": "2.0.0"
+			}
+		},
+		"depd": {
+			"version": "1.1.2"
+		},
+		"destroy": {
+			"version": "1.0.4"
+		},
+		"dotenv": {
+			"version": "8.2.0"
+		},
+		"ee-first": {
+			"version": "1.1.1"
+		},
+		"encodeurl": {
+			"version": "1.0.2"
+		},
+		"escape-html": {
+			"version": "1.0.3"
+		},
+		"etag": {
+			"version": "1.8.1"
+		},
+		"express": {
+			"version": "4.17.1",
+			"requires": {
+				"accepts": "~1.3.7",
+				"array-flatten": "1.1.1",
+				"body-parser": "1.19.0",
+				"content-disposition": "0.5.3",
+				"content-type": "~1.0.4",
+				"cookie": "0.4.0",
+				"cookie-signature": "1.0.6",
+				"debug": "2.6.9",
+				"depd": "~1.1.2",
+				"encodeurl": "~1.0.2",
+				"escape-html": "~1.0.3",
+				"etag": "~1.8.1",
+				"finalhandler": "~1.1.2",
+				"fresh": "0.5.2",
+				"merge-descriptors": "1.0.1",
+				"methods": "~1.1.2",
+				"on-finished": "~2.3.0",
+				"parseurl": "~1.3.3",
+				"path-to-regexp": "0.1.7",
+				"proxy-addr": "~2.0.5",
+				"qs": "6.7.0",
+				"range-parser": "~1.2.1",
+				"safe-buffer": "5.1.2",
+				"send": "0.17.1",
+				"serve-static": "1.14.1",
+				"setprototypeof": "1.1.1",
+				"statuses": "~1.5.0",
+				"type-is": "~1.6.18",
+				"utils-merge": "1.0.1",
+				"vary": "~1.1.2"
+			}
+		},
+		"finalhandler": {
+			"version": "1.1.2",
+			"requires": {
+				"debug": "2.6.9",
+				"encodeurl": "~1.0.2",
+				"escape-html": "~1.0.3",
+				"on-finished": "~2.3.0",
+				"parseurl": "~1.3.3",
+				"statuses": "~1.5.0",
+				"unpipe": "~1.0.0"
+			}
+		},
+		"forwarded": {
+			"version": "0.1.2"
+		},
+		"fresh": {
+			"version": "0.5.2"
+		},
+		"http-errors": {
+			"version": "1.7.2",
+			"requires": {
+				"depd": "~1.1.2",
+				"inherits": "2.0.3",
+				"setprototypeof": "1.1.1",
+				"statuses": ">= 1.5.0 < 2",
+				"toidentifier": "1.0.0"
+			}
+		},
+		"iconv-lite": {
+			"version": "0.4.24",
+			"requires": {
+				"safer-buffer": ">= 2.1.2 < 3"
+			}
+		},
+		"inherits": {
+			"version": "2.0.3"
+		},
+		"ipaddr.js": {
+			"version": "1.9.1"
+		},
+		"media-typer": {
+			"version": "0.3.0"
+		},
+		"merge-descriptors": {
+			"version": "1.0.1"
+		},
+		"methods": {
+			"version": "1.1.2"
+		},
+		"mime": {
+			"version": "1.6.0"
+		},
+		"mime-db": {
+			"version": "1.44.0"
+		},
+		"mime-types": {
+			"version": "2.1.27",
+			"requires": {
+				"mime-db": "1.44.0"
+			}
+		},
+		"ms": {
+			"version": "2.0.0"
+		},
+		"negotiator": {
+			"version": "0.6.2"
+		},
+		"object-assign": {
+			"version": "4.1.1"
+		},
+		"on-finished": {
+			"version": "2.3.0",
+			"requires": {
+				"ee-first": "1.1.1"
+			}
+		},
+		"parseurl": {
+			"version": "1.3.3"
+		},
+		"path-to-regexp": {
+			"version": "0.1.7"
+		},
+		"proxy-addr": {
+			"version": "2.0.6",
+			"requires": {
+				"forwarded": "~0.1.2",
+				"ipaddr.js": "1.9.1"
+			}
+		},
+		"qs": {
+			"version": "6.7.0"
+		},
+		"range-parser": {
+			"version": "1.2.1"
+		},
+		"raw-body": {
+			"version": "2.4.0",
+			"requires": {
+				"bytes": "3.1.0",
+				"http-errors": "1.7.2",
+				"iconv-lite": "0.4.24",
+				"unpipe": "1.0.0"
+			}
+		},
+		"safe-buffer": {
+			"version": "5.1.2"
+		},
+		"safer-buffer": {
+			"version": "2.1.2"
+		},
+		"send": {
+			"version": "0.17.1",
+			"requires": {
+				"debug": "2.6.9",
+				"depd": "~1.1.2",
+				"destroy": "~1.0.4",
+				"encodeurl": "~1.0.2",
+				"escape-html": "~1.0.3",
+				"etag": "~1.8.1",
+				"fresh": "0.5.2",
+				"http-errors": "~1.7.2",
+				"mime": "1.6.0",
+				"ms": "2.1.1",
+				"on-finished": "~2.3.0",
+				"range-parser": "~1.2.1",
+				"statuses": "~1.5.0"
+			},
+			"dependencies": {
+				"ms": {
+					"version": "2.1.1"
+				}
+			}
+		},
+		"serve-static": {
+			"version": "1.14.1",
+			"requires": {
+				"encodeurl": "~1.0.2",
+				"escape-html": "~1.0.3",
+				"parseurl": "~1.3.3",
+				"send": "0.17.1"
+			}
+		},
+		"setprototypeof": {
+			"version": "1.1.1"
+		},
+		"statuses": {
+			"version": "1.5.0"
+		},
+		"toidentifier": {
+			"version": "1.0.0"
+		},
+		"type-is": {
+			"version": "1.6.18",
+			"requires": {
+				"media-typer": "0.3.0",
+				"mime-types": "~2.1.24"
+			}
+		},
+		"unpipe": {
+			"version": "1.0.0"
+		},
+		"utils-merge": {
+			"version": "1.0.1"
+		},
+		"vary": {
+			"version": "1.1.2"
+		}
+	}
+}
diff --git a/6-backend-dev/4-exercise-tracker/package.json b/6-backend-dev/4-exercise-tracker/package.json
new file mode 100644
index 0000000..eb2d24b
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/package.json
@@ -0,0 +1,22 @@
+{
+	"name": "fcc-exercise-tracker",
+	"version": "0.1.0",
+	"description": "A REST API project, part of Free Code Camp's curriculum",
+	"main": "index.js",
+	"scripts": {
+		"start": "node index.js"
+	},
+	"dependencies": {
+		"dotenv": "^8.2.0",
+		"express": "^4.16.4",
+		"cors": "^2.8.5"
+	},
+	"repository": {
+		"url": "https://github.com/freeCodeCamp/boilerplate-project-exercisetracker"
+	},
+	"license": "MIT",
+	"keywords": [
+		"node",
+		"express"
+	]
+}
diff --git a/6-backend-dev/4-exercise-tracker/public/style.css b/6-backend-dev/4-exercise-tracker/public/style.css
new file mode 100644
index 0000000..c5eb36b
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/public/style.css
@@ -0,0 +1,59 @@
+* {
+  box-sizing: border-box;
+}
+
+body {
+  font-family:sans-serif;
+  margin: 25px;
+  color: #222;
+  background-color: #f5f5f5;
+}
+
+h1 {
+  font-weight: bold;
+  
+}
+
+p {
+  max-width: 900px;
+}
+
+form {
+  margin-bottom: 25px;
+  padding: 15px;
+  background-color: #87D37C;
+  display: inline-block;
+  width: 100%;
+  max-width: 340px;
+  border-radius: 5px;
+}
+
+input {
+  display: block;
+  margin-bottom: 10px;
+  padding: 5px;
+  width: 100%;
+  border: 1px solid lightgrey;
+  border-radius: 3px;
+  font-size: 16px;
+}
+
+input[type=submit] {
+  font-size: 16px;
+  border-radius: 3px;
+  background-color: #E4F1FE;
+  border: 1px solid grey;
+  box-shadow: 2px 2px #999;
+  cursor: pointer;
+}
+
+input[type=submit]:hover {
+  background-color: #FFFEC4;
+}
+
+code {
+  font-family: monospace;
+  font-size: 1.2em;
+  background-color: #FFFEC4;
+  padding: 2px;
+}
diff --git a/6-backend-dev/4-exercise-tracker/sample.env b/6-backend-dev/4-exercise-tracker/sample.env
new file mode 100644
index 0000000..c0c68b1
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/sample.env
@@ -0,0 +1 @@
+PORT=3000
\ No newline at end of file
diff --git a/6-backend-dev/4-exercise-tracker/views/index.html b/6-backend-dev/4-exercise-tracker/views/index.html
new file mode 100644
index 0000000..00a7a42
--- /dev/null
+++ b/6-backend-dev/4-exercise-tracker/views/index.html
@@ -0,0 +1,46 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Exercise Tracker | freeCodeCamp</title>
+    <link rel="shortcut icon" href="https://cdn.freecodecamp.org/universal/favicons/favicon.ico"  type="image/x-icon" />
+    <link href="https://fonts.googleapis.com/css?family=Roboto" rel="stylesheet" type="text/css" />
+    <link href="style.css" rel="stylesheet" type="text/css" />
+  </head>
+
+  <body>
+    <div class="container">
+      <h1>Exercise tracker</h1>
+      <form action="/api/users" method="post">
+        <h3>Create a New User</h3>
+        <p><code>POST /api/users</code></p>
+        <input id="uname" type="text" name="username" placeholder="username" />
+        <input type="submit" value="Submit" />
+      </form>
+      <form id="exercise-form" method="post">
+        <h3>Add exercises</h3>
+        <p><code>POST /api/users/:_id/exercises</code></p>
+        <input id="uid" type="text" name=":_id" placeholder=":_id" />
+        <input id="desc" type="text" name="description" placeholder="description*" />
+        <input id="dur" type="text" name="duration" placeholder="duration* (mins.)" />
+        <input id="date" type="text" name="date" placeholder="date (yyyy-mm-dd)" />
+        <input type="submit" value="Submit" />
+      </form>
+      <p>
+        <strong>GET user's exercise log: </strong>
+        <code>GET /api/users/:_id/logs?[from][&amp;to][&amp;limit]</code>
+      </p>
+      <p><strong>[ ]</strong> = optional</p>
+      <p><strong>from, to</strong> = dates (yyyy-mm-dd); <strong>limit</strong> = number</p>
+    </div>
+    <script>
+      const exerciseForm = document.getElementById("exercise-form");
+
+      exerciseForm.addEventListener("submit", () => {
+        const userId = document.getElementById("uid").value;
+        exerciseForm.action = `/api/users/${userId}/exercises`;
+
+        exerciseForm.submit();
+      });
+    </script>
+  </body>
+</html>