The theming system leaves preview and becomes the default, refresh splits into three separate operations, and images secured in OneLake finally make it into the report. Also: dozens of formatting options in the slicer and the matrix.
August 2026 update: themes reach general availability, refresh splits into three operations, and images from OneLake enter the report.
August 2026Executive Summary — What's New This Month
Five minutes of reading that give you the full picture, before diving deep. Published on 18.08.2026.
Modern Visual Defaults and the theme pane are generally available. New reports open on the Fluent 2 base theme. The theme pane is available in both Desktop and the browser, with import and export of custom themes.
A silent change that will break existing themes: Font overrides were removed from the base theme, so the text segment now applies consistently across all visuals.
Refreshing a semantic model splits into three operations: Refresh schema and data, sync schema only, or refresh data only — and also at the level of a single table.
Date picker for slicers left preview, with a new Single date setting that limits it to one date, and clearing the selection from an icon in the header.
OneLake files as an image source in the report. Images in OneLake are used in the image visual, in table and matrix cells, in cards and slicers — and Power BI authenticates as the viewer, without needing anonymous access.
Expanding and collapsing column headers in a matrix In general availability, with the option to set the freeze state of row headers as the report default.
Fabric Apps permissions are loosening: By the end of August, app consumers will need only Read permission on the semantic model instead of Build.
mobile: A rotate-view button on the wrist, and data export to Excel directly from the app — while preserving filtering and row-level security.
14 known bugs and limitations documented in Chapter VI, with a workaround for each.
Estimated reading time · 70 minutes
01
Navigating between topics
the buttons Previous Fnext fixed at the top of the screen. Also available via keyboard shortcut, by swiping on a phone, or by jumping to a topic from the topics list.
02
Questions and practice
At the end of the lesson there's a short quiz with immediate feedback for every question. The button for the test Available in the top bar at any time.
03
Progress is saved
The topic where you stopped and the topics you have read are saved only in your browser. You can close and come back, and reset from the topics list.
How each topic is built
Every topic opens with an explanation why The feature exists — the real-world pain and the vision behind it — and continues into the technical detail. At the end of the lesson: a bugs and workarounds chapter, and a 12-question quiz.
What the lesson covers
August 2026 update, published on August 18.
design
Themes in general availability
Fluent 2 as the default, a full theme pane, and the impact of removing font overrides.
modeling
Split refresh
three separate refresh actions, even at the table level — the tool missing for fixing a schema without paying for a full load.
reporting
OneLake and images
OneLake addresses as an image source in six visual types, with authentication under the viewer's identity.
Slicer and matrix
Dozens of design options
Date picker in GA, the Dropdown and Hierarchy segment in the slicer, expanding and collapsing columns in a matrix.
Mobile and development
Rotation, export, and PBIP
A view-rotation button, export to Excel, and instant loading of external changes to the project.
production
Bugs and workarounds
14 known phenomena, the reason for each, and the fix.
Prerequisite: Getting to know the formatting pane, semantic model and refresh. Anyone who took the July lesson will recognize this as the direct continuation of two topics — themes and modeling in the browser.
Chapter I · Design and Themes
The themes come out of preview
What was experimental in July became the default for every new report.
Why Microsoft introduced this
the pain. Visual consistency across an organization is a matter of trust, not aesthetics. A report where every page looks different creates uncertainty for the reader even when the data is correct — they don't know whether a color difference means something. Until now, consistency was achieved in two poor ways: manual work on every visual, or a JSON file that only one person in the organization knew how to edit.
the vision. To take the theme out of the file and bring it into the interface, so every report creator can define a consistent visual language without writing a line of code — and export it for reuse. In August this becomes generally available and the default, meaning no longer an add-on but the starting point.
What's available now
the ability
details
Base set
New reports open on Fluent 2. You can swap the base palette from the theme pane
Color palettes
Choosing and matching a palette for the whole report
Text styles
Changing fonts and styles in one place
Visual and page properties
Background, border, padding, page size, and wallpaper — for the entire report at once
Import and export
A custom theme is saved as a file and used in other reports or organizational themes
where
Both in Desktop and in the browser — a substantial change from July, when the experience was Desktop-only
Update to the July lesson: Anyone who learned there that Fluent 2 and the theme pane are available only in Desktop — that is no longer true. Both capabilities are GA and in the browser.
Chapter I · Design and Themes
The silent change that will break existing themes
One line in the official announcement, and an impact you'll feel in every report and file.
Font overrides have been removed from the base theme. The meaning: the Text section in the theme pane now applies Consistently across all the visuals, instead of the base theme overriding it in certain visuals.
This sounds like an improvement, and it is one — but it changes the behavior of existing reports. If your organizational theme defined one font and in practice some visuals showed a different font because of an override from the base theme, those visuals may now change appearance.
Check before applyingOpen a copy of the central report and swap the base dataset. Compare page by page before touching production.
Remember the order of precedenceBase theme ← custom theme ← manual formatting on a visual. Manual formatting always wins, so manually formatted visuals simply won't respond.
Reset correctlyto zero Single segment In the format pane, not the whole visual — Reset to default also removes button actions, conditional formatting and field-based images.
Exported at the endOnce the theme sits right, export it to a file and add it to the organizational themes.
✓For those who teach or manage a team: This is the moment to set one organizational theme and roll it out, before every analyst discovers the theme pane on their own and produces five different visual languages.
Chapter II · Modeling and refresh
Semantic model refresh splits into three
The most useful feature this month for anyone managing a model in production.
Why Microsoft introduced this
the pain. Until now, refresh was a single, indivisible operation. Added a column to the source? Full refresh required. Fixed a field's name? Full refresh. In a model with hundreds of millions of rows, that means waiting an hour and burning capacity — to sync a structural change that takes a second.
The deeper problem. The lack of separation between schema and data turned every small structural change into an operational decision. Teams postponed schema fixes to the nightly refresh window, and in the meantime worked with a model that did not match the source.
The three options in the Refresh button
the option
What it does
When to use
Refresh schema and data
The familiar behavior: syncs structure and loads data
A routine refresh, or after a change that touches both
Sync schema only
Syncs the model structure against the source, without loading data
A column was added at the source, a type was changed, a field was added — structural change only
Refresh data only
Loading data without touching the schema
When the structure is stable and you only want up-to-date data
and additionally — table-level refresh. You can perform refresh operations on a single table rather than the whole model. In a model with ten fact tables, that's the difference between a one-minute refresh and a one-hour refresh.
✓How this connects to the July lesson: We learned there that TMDL only changes metadata and doesn't refresh, and that you have to refresh manually after changing a Power Query expression. Now this manual refresh is much cheaper — Sync schema only on the table you touched, instead of a full model refresh.
Chapter III · Reporting, images, and OneLake
OneLake Files as an Image Source
The solution to a problem everyone who's tried to put a logo or employee photo in a report has run into.
Why Microsoft introduced this
The pain, and a big one. Until now, an image in a Power BI report required a URL Accessible anonymously. Not SharePoint, not OneDrive, nothing behind a login. Organizations that wanted to show employee photos, vendor logos, or product images had to choose between two bad options: expose the images to the open internet, or give up.
What Microsoft did. Power BI is now validating In the viewer's name against OneLake. In other words, the images stay secured inside the organization, and anyone without permission simply doesn't see them — without exposing anything outward.
Where it works
01
Image visual
Image visual with a OneLake address as source.
02
Table and matrix
Images inside cells, like a product image column.
03
Card visual
An image in the card, including a hover state added in June.
04
slicers
A button slicer and a list slicer with images.
05
Custom icons
The Icons component in conditional formatting of a table and matrix.
06
maps
A reference layer on the map and Shape map files — they too come from a OneLake address.
Why this changes the architecture: OneLake becomes the report's asset repository, not just its data. Logos, icons, TopoJSON files for sales regions — all in one place, permission-managed, and backed up along with the rest of the items.
Chapter III · Reporting, images, and OneLake
Slicer and matrix — styling and control
The two most common visuals in an enterprise report get dozens of new options.
Date picker for the slicer — now in GA
The feature we taught in June as a preview has reached general availability, with two additions:
the addition
What it does
Single date
A new definition under Visual > Slicer settings > Selection controls that limits the slicer to one date at a time
Cleaning from the header
You can clear the selection from an icon in the slicer header, without opening the calendar
What already existed
Relative selections that roll forward with time, a calendar, and a slider for choosing a range or a single date
New formatting segments in the slicer
Dropdown
A new section in the formatting pane
Dropdown border color, rounded corners, color and transparency of the open icon, and an Accent bar option.
Hierarchy
A new segment added
Coloring the expand/collapse icons in the hierarchical slicer — especially important in dark themes.
matrix
the ability
details
Expanding and collapsing column headers (GA)
+/- icons when there is more than one field in Columns. The color and size can be adjusted under Column headers > +/- icons
Freeze mode by default
Sets the freeze state of row headers under Layout > Freeze, and the definition Saved with the report
Temporary freeze
the right-click freeze options remain, for a one-off change in a session that isn't saved
✓The distinction worth teaching: The setting in the formatting pane is what every reader gets; the right-click is a personal, temporary preference. Until now there was only the second option, so every reader had to freeze it themselves.
Chapter III · Reporting, images, and OneLake
Charts, maps and comments
Finishing touches that save manual tweaking.
01
Outer padding (GA)
A new setting under Layout that controls the gap between the edges of the chart area and the first and last category. For column, bar, line, ribbon and waterfall charts. Zero percent fills the area, and combined with Space between categories set to zero — a full fill.
02
Azure Maps — Shape Matching
The reference layer renders faster, and filtering, cross-highlighting and zoom respond more smoothly. No configuration change needed.
03
Azure Maps — filtering and zoom
When you filter down to a smaller dataset, the map reloads and includes points that were outside the initial 30,000-point limit — and it also automatically focuses on the filtered area.
04
A central value in the donut (GA)
A donut chart shows a value at the center without assuming a card above it. Format, display units, font, labels, images and background — and the value updates with filtering, cross-highlighting, drill-down and slice selection.
05
Reviews in enterprise apps
You can comment on report pages and on visuals inside an enterprise app, start a discussion and tag with @. The comment retains the current report context.
06
Copilot and bookmarks
Copilot Summary and the Copilot Narrative visual now also read visuals that are hidden by default and revealed via bookmark. RLS and OLS continue to be enforced.
For anyone who built a report around the 30,000-point limit in Azure Maps: The behavior changed. A filter that previously returned a partial picture will now return the full data points of the filtered region.
Chapter IV · Permissions, mobile, and development
Fabric Apps — lower-level permission for consumers
A small change in wording, a big one in governance.
By the end of August: Fabric App consumers will need Read only on the semantic model, instead of Build. App creators still need Build.
Why Microsoft introduced this
Why this matters. The Build permission isn't just "view". It allows building new content on top of the model: connecting your own report to it, exporting data, and accessing it through the XMLA endpoint. When an app consumer simply requires Build, the organization has effectively given every end user access far broader than they need — and that's exactly the definition of violating the principle of least privilege.
The change aligns Fabric Apps with what we saw in July in enterprise apps: permissions that match exactly what the user does, and no more.
✓Recommended action: Go over the users who got Build just to consume an app, and downgrade them to Read. This reduces the exposure surface without hurting anyone.
Chapter IV · Permissions, mobile, and development
Mobile and development
Two mobile improvements that field staff will feel immediately, and one for developers.
mobile
View rotation button
button Rotate view In the report's bottom bar on mobile, lets you switch layout with a single tap — Even when the phone is locked in portrait mode. Launched for iOS and Android.
mobile
Exporting to Excel from the app
Exporting data from a visual directly from the mobile app, via focus mode or the three-dot menu. The export reflects the filtering, slicers, drill-down state, and row-level security.
development
Instant loading of PBIP
Power BI Desktop detects external changes to project files and offers to apply them with one click. An entry point was also added that opens the project directly in Visual Studio Code.
connectivity
Accessibility in Power Query
Contrast and readability improvements in the interface across light and dark themes, and connector icons with transparent backgrounds automatically get a white background in dark mode.
Why the rotate button is more than it sounds: We learned that the mobile layout is only shown in portrait mode, and tilting the device brings back the regular layout. Users who lock their phone to portrait mode were stuck with only the mobile layout. The button solves this without disabling the lock.
✓For those working with PBIP and Git: Instant reload closes the loop that started with Desktop Bridge in June. You edit a file in an external editor or an AI agent, and Desktop offers to apply it - without closing and reopening the file.
Chapter V · Messages and Tracking
What must be marked on the calendar
One recurring message worth handling before October.
Starting from October: Users with Power BI Desktop from March 2026 and earlier won't be able to save and share files to OneDrive and SharePoint. You need to update Power BI Desktop to keep this capability. The message has recurred since June and July — about two months left.
What's worth checking in the organization now
To locate old versionsto check who on the team is still on a version from before April 2026. In large organizations this is usually whoever does not have installation permissions.
To check the themesAfter removing the font overrides, open a copy of a key report and make sure the look has not changed.
To remove unnecessary Build permissionsUsers who only consume a Fabric App can be downgraded to Read.
Consider split refresh in processesAny process that does a full refresh just to sync the schema — a candidate for switching to Sync schema only.
✓Downloadable version: The August 2026 version of Power BI Desktop is available in the Microsoft Download Center. It's always recommended to work with the latest version — older versions don't receive support, and can't open files saved in newer versions.
Chapter VI · Bugs and Workarounds
14 known phenomena and the solution for each
Based on the official documentation and on behaviors that users report. It is worth reviewing this before updating in production.
the phenomenon
the reason
The workaround
Fonts changed in an old report after switching to a new base theme
The font overrides were removed from the base theme, so the text section now applies to all the visuals
Test on a copy before production; set the font explicitly in the Text section of the theme pane
I swapped the theme and half the visuals didn't respond
Manual formatting on a visual always overrides the theme
to reset the relevant section in the formatting pane — not Reset to default on the entire visual
Reset to default deleted important settings of mine
Fully resetting a visual also removes button actions, conditional formatting rules, images from a URL or field, and alt text labels
To reset just a single section; before a big reset — save a copy of the report
Existing pages stayed at the old size after switching the base theme
Only new pages get the canvas size of the base theme
Update via the Page section in the theme pane, which applies to all pages at once
OneLake image not displayed in the report
The viewer doesn't have permission for the file, or the format isn't supported
Power BI authenticates as the viewer — make sure there's permission on the Lakehouse or the folder, and use the supported formats
The OneLake address I copied returns an Unauthorized error in the browser
OneLake addresses require authentication; a browser check without a token will always fail
Don't check in the browser — check inside the report itself, where the authentication happens
A column I originally added doesn't appear in the model
Data-only refresh doesn't sync schema
to run Sync schema only or Refresh schema and data, not Refresh data only
Refreshing the entire model takes an hour for one small structural change
A habit from the era when refresh was a single action
Refresh at the single-table level, and Sync schema only when you don't need data
+/- icons don't appear in the matrix's column headers
The capability is only active when there's more than one field in Columns
to add a second field to the column hierarchy; color and size are controlled under Column headers > +/- icons
Freezing row headers is not saved for users
Freezing via right-click is temporary and per-session
Set freeze mode as the default under Layout > Freeze in the formatting pane — this is saved with the report
The Azure map now shows more points than before
The map reloads on filter and includes points that were outside the 30,000-point limit, and also automatically focuses
Intentional behavior. Reports built around the old limitation — check that the conclusions still hold
Fabric App consumers get overly broad access
In the past, Build permission was required, which also allows building on top of the model and exporting
From the end of August, Read is enough. Go over the existing permissions and lower
The mobile layout is stuck showing even when you want the regular one
The device is locked in portrait mode, and the mobile layout loads automatically
button Rotate view In the footer it swaps the layout on click, without releasing the lock
A change I made in an external editor isn't visible in Desktop
Until now, Desktop hasn't detected external changes to PBIP files
From the August version, a prompt is shown to apply the change with one click; if it does not appear — make sure the project is open as PBIP and not as pbix
Chapter VII · Self-check
Quiz — 12 questions
One question at a time. A correct answer is colored green, an incorrect one red, and the correct answer is always revealed along with a full technical explanation.
On which base theme will a new report open, from the August 2026 version?
explanation: With the move to general availability, Fluent 2 went from a preview theme to the default for every new report. In July it was still experimental and required manual activation, in Desktop only. You can still switch the base theme to Classic 2026 or Classic 2018 from the theme pane, for example for consistency with older reports in the organization.
What does removing the base system font overrides mean?
explanation: In the past, the base theme overrode the font setting in certain visuals, so a theme that defined one font didn't always actually get applied. Now the Text section in the theme panel applies uniformly to everything. This is an improvement — but it Changes the behavior of existing reports, so it's essential to test on a copy before applying in production.
You added a new column at the data source. Which refresh operation will sync it most cheaply?
explanation: Sync schema only synchronizes the model structure against the source without loading data — exactly what's needed for a structural change. Refresh data only is the opposite, and so no will bring the column, and that's a common mistake. Refresh schema and data will work but will pay for a full load that isn't needed. In a large model that's the difference between a second and an hour.
What's distinctive about an image sourced from a OneLake address compared to a regular address?
explanation: That's exactly the problem this feature solves. Until now, an image in a report required an anonymously accessible URL — not SharePoint, not OneDrive, nothing behind a login. Organizations were forced to choose between exposing images to the open internet or giving up on them. Now Power BI performs the authentication on the viewer's behalf, so anyone without permission simply doesn't see it — with no external exposure.
The expand/collapse icons for column headers in the matrix aren't showing up. What's probably missing?
explanation: The capability is only active when there’s more than one field in the Columns area — without a hierarchy there’s nothing to expand or collapse. The feature is generally available, so it doesn’t require a preview, and it isn’t related to refresh or permissions. Once there’s a hierarchy, you can control the color and size of the icons under Column headers and then +/- icons.
What's the difference between freezing row headers in the formatting pane versus freezing with a right-click?
explanation: This is the important distinction in the feature. Until now there was only right-click, meaning every reader had to freeze it themselves each time anew. The setting under Layout then Freeze is saved with the report, so it’s what every reader gets by default. Right-click remains as a temporary personal preference, and that’s the right combination.
What permission will Fabric App consumers need on the semantic model starting end of August?
explanation: The change from Build to Read is a significant governance shift. Build isn't just viewing: it allows connecting new reports on top of the model, exporting data, and accessing it through the XMLA endpoint. When an app consumer was required to have Build, the organization was effectively granting every end user far broader access than they needed. App creators still need Build.
What does the Outer padding setting do in a bar chart?
explanation: The setting is under Layout and controls only the spacing at the edges of the chart area. The gap between The categories are controlled by a separate setting called Space between categories, and to fill the chart area completely you need to set both to zero percent. The setting is available for columns, bars, line, ribbon and waterfall.
A user has locked their phone in portrait mode and wants to see the regular layout. What is the fix as of August?
explanation: Until now, the mobile layout loaded automatically in portrait mode, and the only way to get back to the regular layout was to tilt the device — which doesn't work when rotation is locked. The Rotate view button switches layouts with a single tap, without touching device settings. Opening it in a browser will indeed always show the regular layout, but that's a workaround, not the solution this update offers.
You changed the base theme and the existing pages stayed at the old size. Why?
explanation: Switching the base theme doesn't change the size of pages that already exist in the report — deliberate behavior, so as not to break layouts. The solution is the Page section in the theme pane, which updates page size, background color and wallpaper for all pages at once instead of going page by page.
You copied a OneLake address and pasted it into a browser — you get an Unauthorized error. What does that mean?
explanation: This is a common diagnostic mistake. The address requires an auth token, and a browser where you paste the address directly doesn’t send it — even if you’re logged into the service. The correct check is inside the report itself, where Power BI performs the authentication on the viewer’s behalf. And making the file public is exactly what the feature is meant to prevent.
How does this update make working with TMDL, which we learned in July, cheaper?
explanation: In July we learned that TMDL changes metadata only and doesn't refresh, so after a change to a Power Query expression or a calculated column a manual refresh was required — which was costly. Now you can run Sync schema only, even at the level of a single table. TMDL itself hasn't changed and still doesn't refresh — what's changed is price the refresh that follows it.
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Chapter VII · Self-check
Summary and next steps
Ten rows that summarize the lesson.
topic
what to remember
themes
Fluent 2 by default, the theme panel in GA also in the browser, import and export for organizational themes