diff --git a/changelog/upgrade-notes.md b/changelog/upgrade-notes.md
index 088f396158..7cfae9d032 100644
--- a/changelog/upgrade-notes.md
+++ b/changelog/upgrade-notes.md
@@ -2,6 +2,8 @@
 
 ### Next release
 
+### v4.0.0
+
 #### Simpler `ol.source.Zoomify` `url` configuration
 
 Instead specifying a base url, the `url` for the `ol.source.Zoomify` source can now be a template.  The `{TileGroup}`, `{x}`, `{y}`, `{z}` and placeholders must be included in the `url` in this case. the `url` can now also include subdomain placeholders:
diff --git a/changelog/v4.0.0.md b/changelog/v4.0.0.md
new file mode 100644
index 0000000000..d8cb8e3253
--- /dev/null
+++ b/changelog/v4.0.0.md
@@ -0,0 +1,183 @@
+# 4.0.0
+
+Starting with this version, OpenLayers introduces [Semantic Versioning](http://semver.org). Unlike the switch from v2.x to v3.x, which marked a complete rewrite of the library with an entirely new API, major version increments now simply mean that users should pay attention to the *'Breaking changes'* section of the upgrade notes.
+
+For users of mainstream bundlers and minifiers, OpenLayers is now also available as a set of ES2015 modules. See https://npmjs.com/package/ol/. With that package, bundling only the needed parts of the library with an application is now completely hassle free.
+
+Version 4.0.0 includes enhancements and fixes from 107 pull requests since the previous release.
+
+Among these changes, [#6381](https://github.com/openlayers/openlayers/pull/6381) adds an example which shows how to use [geojson-vt](https://www.npmjs.com/package/geojson-vt) for highly efficient rendering of GeoJSON data as vector tiles.
+
+Several improvements were made to `ol.source.Zoomify`, including projection support ([#6387](https://github.com/openlayers/openlayers/pull/6387)) and support for URL templates ([#6475](https://github.com/openlayers/openlayers/pull/6475)).
+
+Also the `ol.source.ImageArcGISRest` saw some enhancements, including HiDPI/Retina support and a fix that avoids non-integer DPI values ([#6300](https://github.com/openlayers/openlayers/pull/6300) and [#6467](https://github.com/openlayers/openlayers/pull/6467)).
+
+On the topic of drawing tools, @tst-ppenev completed an effort to make the `ol.interaction.Modify` interaction support modification of `ol.geom.Circle` geometries ([#6457](https://github.com/openlayers/openlayers/pull/6457)).
+
+
+## Breaking changes
+
+### Simplified `ol.View#fit()` API
+
+In most cases, it is no longer necessary to provide an `ol.Size` (previously the 2nd argument) to `ol.View#fit()`. By default, the size of the first map that uses the view will be used. If you want to specify a different size, it goes in the options now (previously the 3rd argument, now the 2nd).
+
+Most common use case - old API:
+```js
+map.getView().fit(extent, map.getSize());
+```
+Most common use case - new API:
+```js
+map.getView().fit(extent);
+```
+Advanced use - old API:
+```js
+map.getView().fit(extent, [200, 100], {padding: 10});
+```
+Advanced use - new API:
+```js
+map.getView().fit(extent, {size: [200, 100], padding 10});
+```
+
+### Removal of deprecated methods
+
+The deprecated `ol.animation` functions and `map.beforeRender()` method have been removed.  Use `view.animate()` instead.
+
+The `unByKey()` method has been removed from `ol.Observable` instances.  Use the `ol.Observable.unByKey()` static function instead.
+```js
+var key = map.on('moveend', function() { ...});
+map.unByKey(key);
+```
+New code:
+```js
+var key = map.on('moveend', function() { ...});
+ol.Observable.unByKey(key);
+```
+
+## Upgrade notes
+
+### Simpler `ol.source.Zoomify` `url` configuration
+
+Instead specifying a base url, the `url` for the `ol.source.Zoomify` source can now be a template.  The `{TileGroup}`, `{x}`, `{y}`, `{z}` and placeholders must be included in the `url` in this case. the `url` can now also include subdomain placeholders:
+```js
+new ol.source.Zoomify({
+  url: 'https://{a-f}.example.com/cgi-bin/iipsrv.fcgi?zoomify=/a/b/{TileGroup}/{z}-{x}-{y}.jpg'
+});
+```
+
+#### Removed build flags (`@define`)
+
+The `ol.DEBUG`, `ol.ENABLE_TILE`, `ol.ENABLE_IMAGE`, `ol.ENABLE_VECTOR`, and `ol.ENABLE_VECTOR_TILE` build flags are no longer necessary and have been removed.  If you were using these in a `define` array for a custom build, you can remove them.
+
+If you leave `ol.ENABLE_WEBGL` set to `true` in your build, you should set `ol.DEBUG_WEBGL` to `false` to avoid including debuggable shader sources.
+
+
+## List of all changes
+
+ * [#6477](https://github.com/openlayers/openlayers/pull/6477) - Save and restore context when rotating ([@ahocevar](https://github.com/ahocevar))
+ * [#6475](https://github.com/openlayers/openlayers/pull/6475) - Use an url template for ol.source.Zoomify ([@fredj](https://github.com/fredj))
+ * [#6478](https://github.com/openlayers/openlayers/pull/6478) - Update clean-css-cli to the latest version 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6472](https://github.com/openlayers/openlayers/pull/6472) - Use fixed pixel ratio for hit tolerance tests ([@ahocevar](https://github.com/ahocevar))
+ * [#6468](https://github.com/openlayers/openlayers/pull/6468) - Remove console.assert in ol.structs.PriorityQueue tests ([@fredj](https://github.com/fredj))
+ * [#6467](https://github.com/openlayers/openlayers/pull/6467) - Round the DPI value in ol.source.ImageArcGISRest ([@fredj](https://github.com/fredj))
+ * [#6466](https://github.com/openlayers/openlayers/pull/6466) - Small XML error in KML test ([@tchandelle](https://github.com/tchandelle))
+ * [#6410](https://github.com/openlayers/openlayers/pull/6410) - fixed the degreesToStringHDMS_() function to promote a seconds value … ([@rjackson64840](https://github.com/rjackson64840))
+ * [#6461](https://github.com/openlayers/openlayers/pull/6461) - Add button to edit examples in CodePen ([@tchandelle](https://github.com/tchandelle))
+ * [#6320](https://github.com/openlayers/openlayers/pull/6320) - Use the 'openlayers' tag instead of 'openlayers-3' ([@ahocevar](https://github.com/ahocevar))
+ * [#6460](https://github.com/openlayers/openlayers/pull/6460) - Remove ol.Observable#unByKey ([@fredj](https://github.com/fredj))
+ * [#6463](https://github.com/openlayers/openlayers/pull/6463) - chore(package): update clean-css-cli to version 4.0.5 ([@openlayers](https://github.com/openlayers))
+ * [#6459](https://github.com/openlayers/openlayers/pull/6459) - Use ol.coordinate.distance ([@fredj](https://github.com/fredj))
+ * [#6457](https://github.com/openlayers/openlayers/pull/6457) - Add Circle Modification ([@tst-ppenev](https://github.com/tst-ppenev))
+ * [#6455](https://github.com/openlayers/openlayers/pull/6455) - Make all @api annotations imply stability ([@tschaub](https://github.com/tschaub))
+ * [#6452](https://github.com/openlayers/openlayers/pull/6452) - Remove deprecated methods ([@tschaub](https://github.com/tschaub))
+ * [#6361](https://github.com/openlayers/openlayers/pull/6361) - Remove "margin" at the bottom of the canvas ([@tchandelle](https://github.com/tchandelle))
+ * [#6450](https://github.com/openlayers/openlayers/pull/6450) - Update coveralls to the latest version 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6302](https://github.com/openlayers/openlayers/pull/6302) - Publish a package for use with ES module bundlers ([@tschaub](https://github.com/tschaub))
+ * [#6446](https://github.com/openlayers/openlayers/pull/6446) - Update eslint to the latest version 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6445](https://github.com/openlayers/openlayers/pull/6445) - Fix pinch zooming ([@tschaub](https://github.com/tschaub))
+ * [#6444](https://github.com/openlayers/openlayers/pull/6444) - Disallow pinch zooming beyond min/max resolution ([@tschaub](https://github.com/tschaub))
+ * [#6443](https://github.com/openlayers/openlayers/pull/6443) - goog.require cleanup ([@openlayers](https://github.com/openlayers))
+ * [#6439](https://github.com/openlayers/openlayers/pull/6439) - Improve tile render performance ([@ahocevar](https://github.com/ahocevar))
+ * [#6442](https://github.com/openlayers/openlayers/pull/6442) - Fix missing goog.require ([@fredj](https://github.com/fredj))
+ * [#6441](https://github.com/openlayers/openlayers/pull/6441) - Update metalsmith-layouts to the latest version 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6437](https://github.com/openlayers/openlayers/pull/6437) - Fit on circle ([@tchandelle](https://github.com/tchandelle))
+ * [#6427](https://github.com/openlayers/openlayers/pull/6427) - Ensure WMS width and height are always integers ([@ahocevar](https://github.com/ahocevar))
+ * [#6432](https://github.com/openlayers/openlayers/pull/6432) - Use ol.proj.EPSG3857.WORLD_EXTENT in ol.source.TileImage tests ([@fredj](https://github.com/fredj))
+ * [#6424](https://github.com/openlayers/openlayers/pull/6424) - Update dependencies to enable Greenkeeper 🌴 ([@openlayers](https://github.com/openlayers))
+ * [#6422](https://github.com/openlayers/openlayers/pull/6422) - Don't listen twice to move and end events in ol.control.ZoomSlider ([@fredj](https://github.com/fredj))
+ * [#6426](https://github.com/openlayers/openlayers/pull/6426) - Add rewrite_polyfills to custom builds tutorial ([@probins](https://github.com/probins))
+ * [#6365](https://github.com/openlayers/openlayers/pull/6365) - Make enums for draw and modify interactions public ([@gberaudo](https://github.com/gberaudo))
+ * [#6294](https://github.com/openlayers/openlayers/pull/6294) - Update code for closure-compiler v20170124 ([@fredj](https://github.com/fredj))
+ * [#6413](https://github.com/openlayers/openlayers/pull/6413) - Accept ol.StyleFunction in ol.Feature#setStyle() ([@ahocevar](https://github.com/ahocevar))
+ * [#6398](https://github.com/openlayers/openlayers/pull/6398) - Be more tolerant of map and position value ([@fredj](https://github.com/fredj))
+ * [#6399](https://github.com/openlayers/openlayers/pull/6399) - Small doc fix in VectorTileOptions renderMode ([@tchandelle](https://github.com/tchandelle))
+ * [#6396](https://github.com/openlayers/openlayers/pull/6396) - Show current year in attribution in "HERE Map Tile API" example ([@chrismayer](https://github.com/chrismayer))
+ * [#6390](https://github.com/openlayers/openlayers/pull/6390) - Tag deprecated functions with @deprecated ([@fredj](https://github.com/fredj))
+ * [#6370](https://github.com/openlayers/openlayers/pull/6370) - Feature apidoc, fix events and observable properties ([@tchandelle](https://github.com/tchandelle))
+ * [#6376](https://github.com/openlayers/openlayers/pull/6376) - Make ol.format.filter.or/and accept n filter conditions ([@tsauerwein](https://github.com/tsauerwein))
+ * [#6393](https://github.com/openlayers/openlayers/pull/6393) - Only stop animation when animating ([@ahocevar](https://github.com/ahocevar))
+ * [#6387](https://github.com/openlayers/openlayers/pull/6387) - Add projection option to ol.source.Zoomify ([@ahocevar](https://github.com/ahocevar))
+ * [#6386](https://github.com/openlayers/openlayers/pull/6386) - Snap : only listen to change event triggered by the feature ([@tchandelle](https://github.com/tchandelle))
+ * [#6383](https://github.com/openlayers/openlayers/pull/6383) - Modify interaction: check if interaction is active before drawing modifying vertex ([@tchandelle](https://github.com/tchandelle))
+ * [#6381](https://github.com/openlayers/openlayers/pull/6381) - geojson-vt integration example ([@drnextgis](https://github.com/drnextgis))
+ * [#6373](https://github.com/openlayers/openlayers/pull/6373) - Use the ol.DEBUG_WEBGL flag to debug shader sources ([@tschaub](https://github.com/tschaub))
+ * [#6379](https://github.com/openlayers/openlayers/pull/6379) - Set the overview map target in ol.control.OverviewMap.setMap ([@fredj](https://github.com/fredj))
+ * [#6375](https://github.com/openlayers/openlayers/pull/6375) - Use present in license text ([@bartvde](https://github.com/bartvde))
+ * [#6371](https://github.com/openlayers/openlayers/pull/6371) - Adjust copyright to include 2017 ([@kolosov-sergey](https://github.com/kolosov-sergey))
+ * [#6364](https://github.com/openlayers/openlayers/pull/6364) - Make sure moveTo is called after beginPath ([@ahocevar](https://github.com/ahocevar))
+ * [#6285](https://github.com/openlayers/openlayers/pull/6285) - Make size argument of ol.View#calculateExtent() optional ([@ahocevar](https://github.com/ahocevar))
+ * [#6357](https://github.com/openlayers/openlayers/pull/6357) - Fix GeoJSONCRSCode definition ([@fredj](https://github.com/fredj))
+ * [#6362](https://github.com/openlayers/openlayers/pull/6362) - Remove empty file ([@fredj](https://github.com/fredj))
+ * [#6358](https://github.com/openlayers/openlayers/pull/6358) - Ensure polygons without stroke are fully filled ([@ahocevar](https://github.com/ahocevar))
+ * [#6356](https://github.com/openlayers/openlayers/pull/6356) - Bring custom builds tutorial up to date ([@probins](https://github.com/probins))
+ * [#6359](https://github.com/openlayers/openlayers/pull/6359) - When applying a pending fill, also apply a pending stroke ([@ahocevar](https://github.com/ahocevar))
+ * [#6360](https://github.com/openlayers/openlayers/pull/6360) - Remove ol.array.flatten function ([@openlayers](https://github.com/openlayers))
+ * [#6353](https://github.com/openlayers/openlayers/pull/6353) - API doc : add highlight style to the active anchor ([@tchandelle](https://github.com/tchandelle))
+ * [#6355](https://github.com/openlayers/openlayers/pull/6355) - Remove test.geojson which was accidently committed in 57342a6 ([@ahocevar](https://github.com/ahocevar))
+ * [#6349](https://github.com/openlayers/openlayers/pull/6349) - Better documentation for icon-color example ([@ahocevar](https://github.com/ahocevar))
+ * [#6351](https://github.com/openlayers/openlayers/pull/6351) - Only consider pointerdown event if the last pointerup has been emitted ([@tchandelle](https://github.com/tchandelle))
+ * [#6345](https://github.com/openlayers/openlayers/pull/6345) - Mitigate rounding errors in GetMap width/height calculation ([@giohappy](https://github.com/giohappy))
+ * [#6344](https://github.com/openlayers/openlayers/pull/6344) - No special raster reprojection handling for Chrome ([@ahocevar](https://github.com/ahocevar))
+ * [#6339](https://github.com/openlayers/openlayers/pull/6339) - Code cleanup ([@fredj](https://github.com/fredj))
+ * [#6337](https://github.com/openlayers/openlayers/pull/6337) - Constrain center in DragZoom interaction ([@tchandelle](https://github.com/tchandelle))
+ * [#6336](https://github.com/openlayers/openlayers/pull/6336) - Remove unused ol.format.Feature.getExtensions function ([@fredj](https://github.com/fredj))
+ * [#6333](https://github.com/openlayers/openlayers/pull/6333) - Use API key for Thunderforest resources ([@ahocevar](https://github.com/ahocevar))
+ * [#6300](https://github.com/openlayers/openlayers/pull/6300) - Add missing hidpi option for ol.source.ImageArcGISRest ([@fredj](https://github.com/fredj))
+ * [#6109](https://github.com/openlayers/openlayers/pull/6109) - Export Map as PNG (IE issue) ([@NaveenKY](https://github.com/NaveenKY))
+ * [#6332](https://github.com/openlayers/openlayers/pull/6332) - Constrain the center in zoomByDelta ([@tchandelle](https://github.com/tchandelle))
+ * [#6331](https://github.com/openlayers/openlayers/pull/6331) - Remove unused map parameter from ol.interaction.Interaction ([@tchandelle](https://github.com/tchandelle))
+ * [#6326](https://github.com/openlayers/openlayers/pull/6326) - Add lineDashOffset to stroke style ([@tchandelle](https://github.com/tchandelle))
+ * [#6328](https://github.com/openlayers/openlayers/pull/6328) - ol.geom.polygon documentation update on the coordinates format ([@quentin-ol](https://github.com/quentin-ol))
+ * [#6324](https://github.com/openlayers/openlayers/pull/6324) - Ensure resolution stays in range when pinching ([@tschaub](https://github.com/tschaub))
+ * [#6329](https://github.com/openlayers/openlayers/pull/6329) - Fix WMTS theme location for sea-levels layer ([@thomasmoelhave](https://github.com/thomasmoelhave))
+ * [#6323](https://github.com/openlayers/openlayers/pull/6323) - Fix typo in Introduction ([@hdsnet](https://github.com/hdsnet))
+ * [#6305](https://github.com/openlayers/openlayers/pull/6305) - Moved hit Tolerance parameter to own example. ([@KlausBenndorf](https://github.com/KlausBenndorf))
+ * [#6319](https://github.com/openlayers/openlayers/pull/6319) - Remove the '3' from OpenLayers ([@ahocevar](https://github.com/ahocevar))
+ * [#6314](https://github.com/openlayers/openlayers/pull/6314) - WebGL conditional compilation ([@ahocevar](https://github.com/ahocevar))
+ * [#6313](https://github.com/openlayers/openlayers/pull/6313) - Remove ol.DEBUG ([@tschaub](https://github.com/tschaub))
+ * [#6317](https://github.com/openlayers/openlayers/pull/6317) - Update sinon to version 1.17.7 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6312](https://github.com/openlayers/openlayers/pull/6312) - Make layers responsible for creating layer renderers ([@tschaub](https://github.com/tschaub))
+ * [#6308](https://github.com/openlayers/openlayers/pull/6308) - Dedicated modules for shared enums ([@tschaub](https://github.com/tschaub))
+ * [#6307](https://github.com/openlayers/openlayers/pull/6307) - Dedicated modules for enums ([@tschaub](https://github.com/tschaub))
+ * [#6297](https://github.com/openlayers/openlayers/pull/6297) - Update resemblejs to version 2.2.3 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6296](https://github.com/openlayers/openlayers/pull/6296) - Fix #6295. Update reference link in sphere.js ([@jbelien](https://github.com/jbelien))
+ * [#6255](https://github.com/openlayers/openlayers/pull/6255) - Don't reset the css cursor if it's not needed ([@fredj](https://github.com/fredj))
+ * [#6290](https://github.com/openlayers/openlayers/pull/6290) - Use interim tiles ([@ahocevar](https://github.com/ahocevar))
+ * [#6291](https://github.com/openlayers/openlayers/pull/6291) - Document olx.AtPixelOptions#hitTolerance default value ([@fredj](https://github.com/fredj))
+ * [#6283](https://github.com/openlayers/openlayers/pull/6283) - Avoid modifying coordinate in forEachLayerAtCoordinate ([@tschaub](https://github.com/tschaub))
+ * [#6278](https://github.com/openlayers/openlayers/pull/6278) - Add missing require for ol.View ([@tschaub](https://github.com/tschaub))
+ * [#6280](https://github.com/openlayers/openlayers/pull/6280) - Continue loading tiles when image is not ready yet ([@ahocevar](https://github.com/ahocevar))
+ * [#6277](https://github.com/openlayers/openlayers/pull/6277) - Name modules more like their provide ([@tschaub](https://github.com/tschaub))
+ * [#6264](https://github.com/openlayers/openlayers/pull/6264) - Remove the requirement to provide a size to ol.View#fit() ([@ahocevar](https://github.com/ahocevar))
+ * [#6274](https://github.com/openlayers/openlayers/pull/6274) - Update clean-css to version 3.4.23 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6269](https://github.com/openlayers/openlayers/pull/6269) - Update derequire to version 2.0.6 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6270](https://github.com/openlayers/openlayers/pull/6270) - Add a magnify example ([@tschaub](https://github.com/tschaub))
+ * [#6261](https://github.com/openlayers/openlayers/pull/6261) - Fit Zoomify view to image extent ([@ahocevar](https://github.com/ahocevar))
+ * [#6259](https://github.com/openlayers/openlayers/pull/6259) - Simplify Zoomify example ([@ahocevar](https://github.com/ahocevar))
+ * [#6260](https://github.com/openlayers/openlayers/pull/6260) - Enhance documentation for ol.View#fit ([@marcjansen](https://github.com/marcjansen))
+ * [#6258](https://github.com/openlayers/openlayers/pull/6258) - Set geometry name properly ([@ahocevar](https://github.com/ahocevar))
+ * [#6251](https://github.com/openlayers/openlayers/pull/6251) - Take image pixel ratio into account for rendered resolution ([@ahocevar](https://github.com/ahocevar))
+ * [#6244](https://github.com/openlayers/openlayers/pull/6244) - Enforces spacing around commas ([@fredj](https://github.com/fredj))
+ * [#6246](https://github.com/openlayers/openlayers/pull/6246) - Re-render vector tiles when layer has changed ([@ahocevar](https://github.com/ahocevar))
+ * [#6243](https://github.com/openlayers/openlayers/pull/6243) - Consistent spacing between keys and values in object literal ([@fredj](https://github.com/fredj))
+ * [#6238](https://github.com/openlayers/openlayers/pull/6238) - Update eslint to version 3.12.1 🚀 ([@openlayers](https://github.com/openlayers))
+ * [#6236](https://github.com/openlayers/openlayers/pull/6236) - Update clean-css to version 3.4.22 🚀 ([@openlayers](https://github.com/openlayers))